Apparent field of view
Also called: AFOV, apparent field.
How wide an eyepiece's view looks to your eye, in degrees: about 50° for a Plössl, 82° or more for ultra-wides.
Look through an eyepiece at a bright wall: the circle you see spans its apparent field. A wider apparent field gives a bigger piece of sky at the same magnification — more “spacewalk”, and more time before a Dobsonian's target drifts out of view.