Save the Drawing

To prevent losing any data of your work, it's important to save frequently

Quick Save

Quick Access Toolbar > Save

This will saved without prompting for the name or location

Quick Access Toolbar > Save As

This will saved with prompting for the name and location

Automatic Save

The default Auto Save for AutoCAD is 10 mins
Auto Save file extension is *.SV$

AutoCAD also create a backup copy every time you save
Backup file extension is *.BAK

Save in Different Version

Quick Access Toolbar > Save As