Checking is the type of account at your bank. You have two options when you create an account, Checking (meaning you write checks from it) and Savings (meaning you generally don't take money out... or at least as frequently as you would in a checking account). Savings sometimes get better rates because the money is more stable.
When you created the account to link for payouts, you had a selection at one point to identify if it was a checking or savings account. No idea if it actually matters, I've never tried it with the wrong classification of account.