Conversation so far:
What is Tin Pan Alley?
The name originally referred to a specific place: West 28th Street between Fifth and Sixth Avenues in the Flower District of Manhattan.
What did George Gershwin do in Tin Pan Alley?
George Gershwin found his first job as a song plugger.

Question: What is a plugger?
Self-contained rewrite: What is a song plugger?