What's the difference between a 301 Redirect and a 302 Redirect?
A 301 Redirect tells search engines when a page has been permanently moved to a new location. A 302 Redirect tells search engines when a page has been temporarily moved.
This idea may be best explained with the following illustration.
If you moved your store you would put up a sign on the door letting people you know you've permanently moved to a new location.
If you went out to lunch, you would put up a sign letting people know when you'd be back.
In almost all cases you want to make sure you're using a 301 Redirect instead of a 302 Redirect!