Its called Object Snaps and the shortcut toggle is "F3"
you can customize which snap types are active if you right click the Osnaps button near the command line and choose settings... you should also be able to find them in a pull down menu...
Most of the time the only snaps settings I have active are "Center" and occasionally "Midpoint" when using CADduct items... you can also access them during commands by shift-right clicking and choosing the appropriate Osnap from the menu if you need to use any settings that are not currently active...