Fame
Most teachers simply do their thing and their names are never known but to those whose lives they touch personally. However, the occasional professor does make a bit of a name for him- or herself, generally due to books they have written, or to advancements or discoveries they have made in their chosen field not directly related to their lectures.
Familiar with the names Toni Morrison? John Nash? Stephen Hawking? Jessica Simpson? Noam Chomsky? All professors. (Just seeing if you're paying attention. Jessica Simpson was never a professor.)