The word "abstract" relates to anything that departs from reality. From the Renaissance period (1400 - 1700) until the middle of the 19th century, "fine art" was considered to be the representation of the artist's perspective -- reality as viewed and painted by the artist. However, with the arrival of the 20th century, artists began looking for new ways to express modern intellectualism and the blossoming concepts of philosophy and science. The result was Abstract Art, which uses lines, colors, and geometrical forms.
Total abstraction bears no resemblance to anything in particular, but instead invites the viewer to see what he or she will. Among the most popular abstract artists, you'll find Salvador Dali, Pablo Picasso, Jackson Pollock, and Wassily Kandinsky.