What's the difference between "it's" and "its"?

Whats the difference between "its" and "its"
Q:
Help! How do I know when to use "its" and when to use "it’s"?
A:
We get this question all the time and we thought: Hey, our Twitter followers are pretty smart, maybe they have a great way to remember how to tell "its" and "it’s" apart!

True enough, they do!