How to use extrude command to create 3D objects

The EXTRUDE command is used to create 3D solid or surface by extruding the dimension of selected object. For example, a circle can become a cylinder, a line can become a 3D plane, and a rectangle can become a box.

Confusing concepts in CAD

There are some similar concepts in CAD which can be confusing. Hope this post provides clues as to their differences.