Abstract art is a collective term for artistic movements of the 20th century that come into appearance after 1900.
It uses the visual design tool partly - like Cubism - abstractin from the object, sometimes completely detached from nature and real objects (nonrepresentational art).
Works of the first category show abstracted ("focussed", to an essence compressed) objects, characters, spaces. Works of the latter category operate autonomously with visual, artistic means, without any relation to objects.
In the spread of photography with its new quality of the representation of nature one may see the reasons for the emergence of abstract art.