what does jokes mean in slang

In a Grammar class:
Teacher: 'He' does not like girls. What is 'He' in this sentence?
Pappu: Gay.

Rajnikanth does not wear a watch because he sets his own time.

Does Rajniknath smoke?
No, he just fires.

Banta: Does an apple a day really keep the doctor away?
Santa: If you aim it well enough!

Santa: How does a married man celebrates a noiseless Diwali?
Banta: By going abroad?
Santa: No. By sending his wife to her parents' place!
Happy Diwali!