estate agent vs Realtor

estate agent and Realtor both are nouns.

Word	Noun	Adjective	Verb	Adverb
estate agent	Yes	No	No	No
Realtor	Yes	No	No	No

As nouns, Realtor is a hyponym of estate agent; that is, Realtor is a word with a more specific, narrower meaning than estate agent:

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

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