A portrait is a representation of a particular person. A self-portrait is a portrait of the artist by the artist
Portraiture is a very old art form going back at least to ancient Egypt, where it flourished from about 5,000 years ago. Before the invention of photography, a painted, sculpted, or drawn portrait was the only way to record the appearance of someone.
But portraits have always been more than just a record. They have been used to show the power, importance, virtue, beauty, wealth, taste, learning or other qualities of the sitter. Portraits have almost always been flattering, and painters who refused to flatter, such as William Hogarth, tended to find their work rejected. A notable exception was Francisco Goya in his apparently bluntly truthful portraits of the Spanish royal family.
Among leading modern artists portrait painting on commission, that is to order, became increasingly rare. Instead, artists painted their friends and lovers in whatever way they pleased. Most of Picasso’s pictures of women, for example, however bizarre, can be identified as portraits of his lovers. At the same time, photography became the most important medium of traditional portraiture, bringing what was formerly an expensive luxury product affordable for almost everyone. Since the 1990s artists have also used video to create living portraits. But portrait painting continues to flourish.