Auto

Toolbar / Icon:
       
Menu: Snap > Auto
Shortcut: S, A
Commands: snapauto | sa

Description:

The auto snap tool snaps to the closest intersection point, end point, middle point, perpendicular point, reference point, grid point or point on an entity in that order of priority.
The types of reference points the auto snap tool snaps to can be configured under Edit > Application Preferences > Snap > Auto snap.