What is an interrogative and imperative sentence?

Interrogative - Sentence that asks a question:

"What is the use of a house if you haven't got a tolerable planet to put it on?"
(Henry David Thoreau)

Imperative Sentence - A sentence that gives advice or instructions or that expresses a request or command.

"All hope abandon, ye who enter here!"
(Dante Alighieri, The Divine Comedy)