A compass is a drawing instrument used for drawing circles and arcs. It has two legs, one with a point and the other with a pencil or lead. You can adjust the distance between the point and the pencil and that setting will remain until you change it.

Along with a straightedge, the compass is used extensively in constructions, where geometric operations are carried out by drawing only, with no calculations involved.
See Constructions using a straightedge and compass

This kind of compass has nothing to do with the magnetic compass used find the north direction when you are lost.

Pages referring to 'compass'

Definition and meaning of the math word construction. Includes a list of other pages that refer to this word
A brief introduction to constructions - creating various geometric objects with only compasses and straightedge or ruler. History and origins
A list of the compass and straightedge construction worksheets available on this site