Eyepieces are multi-lens components that allow you to achieve different magnifications with your telescope. You cannot start observing with just a telescope and no eyepieces.
The shorter the focal length of the eyepiece, the higher magnifications it produces. It makes sense to have eyepieces in a range of focal lengths, preferably a reasonable selection which takes you in even steps from low to high magnification - to equip you for all the different types of observing and astronomical objects.
Type of build
Plössl
Super Wide Angle SWA
Ultra Wide Angle UWA
Extreme Wide Angle XWA
zoom eyepiece
Reticle eyepieces