A capital is the upper end of a column, pillar or pilaster. Capitals originate from Greek antiquity and can be divided into three widespread orders.
Doric capitals are very simple and only widen towards the top. Ionic capitals end in two volutes and Corinthian capitals have a finial with acanthus ornamentation.
Apart from these three orders of columns, there are several others and also numerous variations. For example, Empire furniture often used engraved brass rings as capitals and pilaster shafts of Biedermeier furniture often end in caryatid busts at the top.
The photo shows a capital of the Corinthian order.