Civil 3D Description Key Basics (Part 1)

I’m surprised that after all these years there are folks who are not fully aware of how description keys work in Civil 3D. This is my attempt to better clarify them.  

This is part 1 of a series explaining how Civil 3D description keys work and how to manage them:

This the link to part 2 of the series:  Civil 3D Description Key Basics (Part 2)