Answer:
Some are clean and some are dirty, but all are meant to get a chuckle. Most like it, some takes offense from it.
It is the time in your life when you simultaneously know everything and nothing at an instance.
What weighs less than blue ?
What doesn't exist, but has a name?
What do elves do after school?
Why did the stadium get so hot after the game?
Funny
Animal
Difficult
Easy
Food
Kids
Logic
What am I?