What is Catnip?

Catnip (the stuff that makes cats go mad) is a type of a certain herb, can anyone tell me what it is?

Thanks in advance,

Ben.

Latin name is Nepeta cataria, it’s a type of mint.

Check this out: http://www.howstuffworks.com/question303.htm

How does catnip work?
The active ingredient is a chemical called Nepetalactone.

I’ve heard it causes a sexual reaction in the cat, kinda like a kitty arphodesiac. I wonder if it’s true.