Eyepiece
Also called: ocular, Plössl, wide-angle eyepiece.
The small lens you look through, which magnifies the telescope's image; its focal length sets the power.
Eyepieces are interchangeable: shorter focal lengths give higher magnification. Besides focal length, two things matter: the apparent field of view (how wide the view looks — 50° in a Plössl, 82–100° in ultra-wides) and eye relief (how far your eye sits from the lens).
They come in 1.25″ and 2″ barrels; the widest low-power fields need 2″ eyepieces.
At the eyepiece
A good kit covers low, medium and high power with a step of about 1.5× between eyepieces.
In AstroPilot
Add your eyepieces under My gear: AstroPilot shows their magnification, exit pupil and field on each telescope, and which to use for each object.