This is often a source of confusion. Many years ago, steel balls were known as “ball bearings”. The term is still used by many people but we, in the bearing trade, call a steel ball a “steel ball” (surprise, surprise!) and to us, a "ball bearing" is a complete assembly with inner and outer ring and balls in-between. This is sometimes referred to as a “ballrace” or a "cartridge bearing" by people outside the bearing trade.
If you want to get technical, the full name of a standard ball bearing such as a skateboard bearing, for example, is a "deep groove radial ball bearing".