Why was i able to buy something with debit card the cleared balance was zero, but account balance had funds

clearly the cheque hadnt cleared yethope makes sense
      Answer1:Some banks are just waiting for you to pull an over draft to hit you with huge fines. If the check didnt clear, since the bank has no idea it is coming soon, you can spend all you want, and then again pay all the fees to the bank, and to the person whose check is going to bounce, their fees. If they try to pass it through the bank twice, you get double the fees from both institutions.Banks also give, and until recently I did not know this, give credit limits on some accounts, they would go five grand on me, I was not happy in case the card was stolen, they would not remove this feature, I found a bank with a smaller amount. I do not want to pay those fees, and interest, that is why I do not any longer have credit cards.
      Answer2:Some banks allow you to make purchases against uncleared funds.If the cheque bounces the bank charges you.The bank wins either way.