Snaps
The types of snaps are:
Sketch Snaps and Quick Snaps are related,
but not identical. Sketch Snaps are global sketch settings that apply
to all sketch commands. Quick Snaps are single, independent selections.
Sketch Snaps
Each Sketch Snap allows you to automatically
snap to selected entities as you sketch. By default, all Sketch Snaps
except Grid
are enabled. You can control all Sketch Snaps through snap options.
Access Sketch Snaps through the Quick
Snaps toolbar, the Quick Snaps 
flyout on the Sketch
toolbar, or the shortcut menu.
Use Sketch Snaps with sketch entities, model edges
in parts, assemblies, and drawings.
On sketches with multiple entities, only the current sketch entity displays
snaps.
To wake up Sketch Snaps:
Create any sketch with multiple entities.
With any sketch tool selected, hover the pointer
over a sketched entity.
The sketch entity changes
color.
The appropriate Quick
Snaps appear on the sketch entity.
The pointer changes,
adding the appropriate inference
information.
Quick Snaps
Quick Snaps are instantaneous, single
operation Sketch Snaps. For example, sketching a line from start to finish
is a single operation. You can double-click any Quick Snaps on the toolbar
to retain the snap capability for multiple instances of the same sketch
entity, or until you select a different Quick Snaps.