I just wanted to expand on this for the moment. Recently, the banks instituted a new policy on 'converting' checks into ACH's. (Automatic debiting) In actual practice, it's like this;
You present the check at a grocery store for $50. The grocery store will 'convert' the check as an ACH and automatically debit your bank account for $50 on the spot or in the same day. You'd better have sufficient funds already existing in the account, or you'll be socked with overdraft fees.
The old (& time-honored method) was to deposit checks into the bank account and 'float' checks at stores, paying bills, etc. Under the same scenario above, a person could write a check to the grocery store, knowing that it will take 3-4 days to clear and by the time it does, your deposits will also have cleared, and everything's nice and tidy at the bank.
This check floating practice is now all but non-existent and dangerous to a healthy bank balance! In today's times, treat checks as if they were ACH's and manage your bank account accordingly. Even better, use debit cards, and just use checks/online payments to pay bills.