It's more what are they. They are ball bearings supported in a ring, permiting similtanious rotation between parts of engineered constructions and are commonly used in automotive, marine and arospace applications. Yeah, I don't know what they are either.
A thrust ball bearing is usually contained in a circular ring and handles an axial load (kind of pushing straight forward), and a roller bearing generally takes the radial load (kind of coming from the sides), which basically equates which way the Force is excerpted.
A thrust bearing is a type of rotary bearing. They allow rotation between 2 parts. They absorb the the axial force which is caused by the unbalance between turbine wheel and compressor wheel. Low quality or OEM turbos typically have 270 degree thrust bearings, high performance turbos have 360 degree thrust bearing. When you go to have a turbo rebuilt it is with the extra money to get a 360 thrust bearing put back in.