While checks do have to obey the laws of gravity, they’re in suspended animation in another sense. A check is basically an IOU. You write someone a check, he or she redeems that check later for cash, and the payment is taken out of your account. Credit cards work in much the same way – you pay for a purchase with your card, and the bill is charged to your account and paid later on.
“Float” is that period of time when a check or credit card charge is in limbo. It’s the time between the moment you write the check and the moment payment is actually received or the moment when a purchase is first charged to your credit card to the moment you pay that bill. During float, the check or credit card charge is, in a sense, suspended. It’s not really performing a function at the moment, but its existence represents a transaction that will have to happen sooner or later. Some people float checks in order to buy time until sufficient money to cover the check appears in their bank account. If this actually happens, great. But if not, the check will bounce and some nasty fees (from the bank and often from the recipient of the check) will start to pile up.