One thing at a time. First, the truffles are a fungus that grows in the ground. I guess that's true.
Mushrooms are also fungi.
But unlike mushrooms, truffles are harder to spot. So people use pigs to find them. March a female pig out around an area where some truffles are growing and the pig will excitedly root them out for you. There's the neat part. It's a chemical truffles produce, probably for several reasons.