The word 'capital' in relation to art is associated with capital letters. All inscriptions used to be in capital letters until the sixth century. These large letters are mainly used in names.  They are also used to begin a sentence. We can see capital letter arts and crafts done by children. 
When used in typography, capital letters are referred to as uppercase letters. Although capital letters seems to be visually powerful, wide use of it is not recommended as it may imply a way of shouting. They are also considered difficult to read.