There are some basic ways to execute a command in CAD system, just like in many other applications in Windows: drop-down menu, toolbar button, Ribbon and shortcut keys such as CTRL + S for Save, CTRL + C for Copy, etc.
The REGION command is used to convert closed objects such as polylines, polygons, circles, ellipses, closed splines, and donuts into two dimensional regions. After we create a region, we can then modify it using various three dimensional tools.
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.