Line entry methods on the command line

I am trying to remember the various ways to enter a line start and end point, on the command line. I remember how to type in the start and end points, but I’ve forgotten the method to type in a relative to selection line, and polar line. Could someone remind me of these line entry methods, and maybe point me to a tutorial on command line entry basics?

Thanks

Hello - see
https://docs.mcneel.com/rhino/7/help/en-us/index.htm#user_interface/keyboard%20modifiers.htm
-Pascal