The best way to look at this is the way another site does it (same process, just labeled differently).

Buyer pays, money goes to your account and is basically a "held" balance. This means buyer has paid, and the item is safe to post. Then the money shifts from that basic "received" status, to an "available for deposit" balance. (This means you essentially have two running balances - a total of money received, and a total of money available for deposit into your account). 

eBay has stated that they guarantee funds that have cleared to them will clear to the seller (in that the payment itself won't bounce or fail, i.e. it's not like a PayPal echeque, where the payment status is only known at the end when it clears or fails - on eBay a payment that hasn't cleared is a payment pending not a payment processing).