AUTOCAD

You can use the LINE  command to draw lines in AutoCAD. 

The LINE command is available in the DRAW PANEL in the ribbon(the menu system) in AutoCAD. 

You can even activate the LINE command by typing "L" in the keyboard and all the commands that start with the letter "L" will appear in the command line. Choose "LINE" from the suggestions. 

Also make sure you have the DYNAMIC INPUT setting switched ON before you start drawing lines or any drawing tools.

Watch the video below to understand how do we draw lines in AutoCAD,