In its most general sense wedding photography is simply any form of photography that relates in any way to weddings. Thus it could include any photographs taken of a couple, together or separately, prior to the event for the purpose of designing invitations, or indeed photos taken during the reception once the marriage ceremony itself has concluded.
However we do tend to think largely in terms of those still group snaps which record for posterity the actual wedding, taken at the venue where the vows were made. Orderly rows of people in immaculately pressed suits and finest dresses, posing for the camera and each subconsciously saying "cheese".
Like all art forms photography has evolved down through the years. An early wedding photograph of the young Queen Victoria and Prince Albert is believed to have been taken in the year 1854, a whole fourteen years after the marriage itself. If this is true, it would have been a re-creation for the camera due to the fact that there had been no photographer at the actual event. The photographic medium had after all only been invented recently, in 1826. In fact such a practice was commonplace, and it wasn't until the 1860s that wedding photographs generally came to be taken at the weddings themselves.
As a result of the crude logistics involved with early wedding photography, it tended at the beginning to be restricted solely to a single photograph of the happy couple themselves. Only later did it become the conventional practice to include group shots of the guests too.
Despite the fact that colour photography came into being back in the early twentieth century, its prohibitive cost meant that for some decades later black and white remained the method most commonly employed. At the same time advancements in technology and greater portability, combined with lower costs, inspired the practice of photographers turning up to weddings uninvited and taking photos which they would then attempt to sell to the participants. It was this "competition" which persuaded professionals involved with the industry to leave their studios and to offer full on-site services.
Today in the age of digital technology photography is more accessible and affordable than previously, but with the wedding being such a special and unique event in a person's life it is still typical to engage a dedicated expert specifically for the purpose. With location being an important factor in the field some local knowledge can also be an asset, and so for example someone requiring wedding photography in Devon is likely to specifically employ a Devon wedding photographer for the task in hand.