3 ways to save a file...

I am not sure if everyone knows this but there are three ways to save a file you are working on. I will start off with the one you are most familiar with.

Quick Save
This is the most common one. The one you do when either hitting the save icon at the top of your screen or doing a "Ctrl+S". This basically just saves the file you are working on while you keep working on it. Pretty simple.

Save As
This is useful option when copying a file. It takes the file you are in and saves it as a completely different file without modifying the original and makes this new copy the active drawing. You can perform this with a "Ctrl+Shift+S". This is also a way to save down to an older version of AutoCAD.

Save
This is an underused command. I find it perfect for making backups or archiving files. What this command does is take the file you are working in and saves a copy as a completely new file, just like Save As. What makes this different than Save As is that you are not active in this new file, you are still in the original file. I find it perfect when working on major design changes and you want to save different iterations of your design. By using the SAVE command you can "backup" before making any major changes. Try it out!