In 1903 Kodak introduced the No. 3A Folding Pocket Kodak. The camera, designed for postcard-size film, allowed the general public to take photographs and have them printed on postcard backs. They are usually the same size as standard vintage postcards (3-1/2" x 5-1/2"). Also known by the acronym "RPPC".
Kodak's 3A camera pioneered in its use of postcard-size film but was not the only one to make Real Photo postcards. Many other cameras were used, some of which used old-fashioned glass plates that required cropping the image to fit the postcard format. According to this site, Kodak "created a service called “Real Photo postcards,” enabling people to make a postcard from any picture they took" in 1907.
While Kodak was certainly the major promoter of photo postcard production, they didn't seem to originate the term "Real Photo," and used it less frequently than photographers and others in the marketplace from 1903 to ca. 1930. But it has become the popular term nowadays to distinguish photographic postcards from commercially printed, mass-produced postcards of the same era. Old House Journal states "Beginning in 1902 Kodak offered a preprinted card back that allowed postcards to be made directly from negatives."  Regardless of when the year, this "technology" allowed photographers to travel from town to town and document life in the places they visited. Old House Journal continues: "Local entrepreneurs hired them to record area events and the homes of prominent citizens. These postcards documented important buildings and sites, as well as parades, fires, and floods. Realtors used them to sell new housing by writing descriptions and prices on the back. Real Photo postcards became expressions of pride in home and community, and were also sold as souvenirs in local drug stores and stationery shops."
Real Photo postcards may or may not have a white border, or a divided back, or other features of postcards, depending on the paper the photographer used. Many current Real Photo postcards are reproductions of earlier historic photos. Want to know if it is authentic or a reproduction: look at it under a magnifying glass. If it is authentic "it will show smooth transitions from one tone to another."  According to the 2Buds, the way to tell is, while looking under the magnifying glass notice that "Postcards that are NOT Real Photos are made up of many small dots. If you look at a Real Photo postcard, the image is solid (no dots)."
From Wikipedia, the free encyclopedia.

Court card or court sized card was the name given to a size of picture postcard, mainly used in the United Kingdom, which were approximately 4.75 x 3.5 inches and predates the standard size of 5.5 x 3.5 inches [Coysh, A.W. - The Dictionary of Picture Postcards in Britain 1894-1939, 1984]. Court cards were smaller and squarer in shape than later cards and were used from about 1894 to 1902[Smith, Phil & Dave - Picture Postcard Values 2005]. In keeping with the regulations of the time, they had an undivided back for the address only and the message had to be written on the 'front' of the card. Many fine examples of these still exist and are sought after by postcard collectors and philatelists alike. Although mainly used in the UK, many were printed by chromolithography in Germany.
From Wikipedia, the free encyclopedia.

   Deltiology is the study and collection of postcards. Compared to philately, the identification of a postcard's place and time of production can often be an impossible task because postcards, unlike stamps, are produced in a decentralised, unregulated manner. For this reason, serious collectors may choose to limit their acquisitions to cards by specific artists and publishers, or by time and location.
Identification
That being said, there are some general rules to dating when a postcard was printed. Postcards are generally sent within a few years of their printing so the postmark helps date a postcard. If the card is original and not a reprint, a postcard's original printing date can be deduced from such things as the fashions worn by people in the card, the era in which the cars on the street were made, and other time sensitive clues.
Practice
Postcards are collected by historical societies, libraries and genealogical societies because of their importance in research such as how a city looked at a particular time in history as well as social history. Many elementary schools use postcards to teach children geography. Postcard Penpal programs have been established to help children in language arts. Deltiologists, as postcard collectors are called, collect for a variety of reasons. Some are attracted to the postcards themselves and then narrow down their interests. Others are interested in something in particular, such as Ballet, and then decide to collect Ballet related postcards as a way to argument their interest in Ballet.
Worldwide Popularity
Worldwide, deltiology is the third largest hobby after stamp collecting and money collecting. As a result, there are postcard clubs all around the world. These clubs, as well as related organizations, host postcard shows on a regular basis.
From Wikipedia, the free encyclopedia.

   A postcard or post card is a rectangular piece of thick paper or thin cardboard intended for writing and mailing without an envelope and at a lower rate than a letter. Stamp collectors distinguish between postcards (which require a stamp) and postal cards (which have the postage pre-printed on them). While a postcard is usually printed by a private company, individual or organization, a postal card is issued by the relevant postal authority.
The study and collecting of postcards is termed deltiology. In the art world the postcard can also be translated into an art object. The art form is called mail art.

Applique - A term used to describe a postcard which has some form of cloth, metal or other embelishment attached to it.
Art Deco - Artistic style of the 1920s, recognisable by its symmetrical designs and straight lines.
Art Nouveau - Artistic style of the turn of the century, characterised by flowing lines and flowery symbols, yet often depicting impressionist more than representational art.
Bas Relief - Postcards with a heavily raised surface, giving a papier-mache appearance.
Composites - A number of individual cards, that when placed together in a group, form a larger picture.
Court Cards - The official size for British postcards between 1894-1899, measuring 115mm x 89mm.
Divided Back - Postcards with a back divided into two sections, one for the message, the other for the address. British cards were first divided in 1902 and American cards in 1907.
Early - A term loosely used to describe any card issued before the Divided Back was introduced.
Embossed - Postcards with a raised surface.
Hold-to-Light- Also referred to as 'HTL', postcards often of a night time scene with cut out areas to show the light.
Intermediate Size - The link between Court Cards and Standard Size, measuring 130mm x 80mm.
Kaleodoscopes - Postcards with a rotating wheel that reveals a myriad of colours when turned.
Midget Postcards - Novelty cards of the size 90mm x 70mm.
Novelty - Any postcard which deviates in any way from the norm. Cards which do something, or have articles attached to them, or are printed in an unusual size or on strange materials. An example is cards made of leather
Oilette - A trade name used by Raphael Tuck to describe postcards reproduced from original paintings.
Real Photographic - Abbreviated to 'RP'. Used to describe postcards produced by a photographic rather than a printing process.
Reward Cards - Cards that were given away to school children for good work.
Standard Size - Introduced in Britain in November 1899, measuring 140mm x 89mm.
Topographical - A term used to describe postcards showing street scenes and general views.
Undivided Back - Describes postcards with a plain back where all of this space was used for the address. This is a term often used to describe Early cards, although undivided were still in common use up until 1907.
Vignette - Usually found on undivided back cards, consisting of a design which does not occupy the whole of the picture side. Vignettes may be anything from a small sketch in one corner of the card, to a design cover three quarters of the card. The purpose is to leave some space for the message to be written, as the entire reverse of the card could only be used for the address.
Write-Away - Used to describe a card with the opening line of a sentence, which the sender would then complete. Often found on early comic cards.
From Wikipedia, the free encyclopedia.