Realtor vs real estate broker

Realtor and real estate broker both are nouns.

Word	Noun	Adjective	Verb	Adverb
Realtor	Yes	No	No	No
real estate broker	Yes	No	No	No

As nouns, real estate broker is a hypernym of Realtor; that is, real estate broker is a word with a broader meaning than Realtor:

Realtor: a real estate agent who is a member of the National Association of Realtors
real estate broker: a person who is authorized to act as an agent for the sale of land

Other hypernyms of Realtor include estate agent, house agent, land agent, real estate agent.

Realtor (noun)	real estate broker (noun)
a real estate agent who is a member of the National Association of Realtors	a person who is authorized to act as an agent for the sale of land