Abstract art is art that does not attempt to represent an accurate depiction of a visual reality but instead use shapes, colours, forms and gestural marks to achieve its effect
Strictly speaking, the word abstract means to separate or withdraw something from something else.
The term can be applied to art that is based an object, figure or landscape, where forms have been simplified or schematised.
Since the early 1900s, abstract art has formed a central stream of modern art.
Art Terms, www.tate.org.uk, glossary