Well, read on. The small circular metallic component that resembles a doughnut and is designed to allow two objects to rotate around a shaft at different speeds or in different directions. A bearing is comprised of an inner race, outer race, balls, cage, shield or seal, and lube.
Some bearings have a snap ring.
See below on how to clean. The system devised by the Annular Bearing Engineering Council to rate the precision of the bearings manufacture. The higher the ABEC number, the tighter the manufacturing tolerances are held. Smaller wheels are slower, and are used more for street or trick skating, while larger wheels are faster and are used more for recreational to speed skating. Get bigger wheels if you want to go faster, smaller if you want to turn more, do tricks etc.