Warm reset is holding the up button (on the 5 way pad), take the battery out, put the battery back in, and keep holding the up button for another minute.
This takes the phone into "safe mode" where you can try deleting a problematic program before doing a soft reset by just pulling the battery out.
A Hard reset is the same process as a warm reset but you are holding the power button. When you let go after a minute it will ask you to push up to delete all data.