Symbols
In UML 2 the components are represented by a rectangle. This may have a visual stereotype in the top right of the rectangle of a small rectangle with two even smaller rectangles jutting out on the left.
The lollipop, a small circle on a stick represents an implemented or provided interface. The socket symbol is a semicircle on a stick that can fit around the lollipop. This socket is a dependency or needed interface.
Read more about this topic: Component Diagram