What is the difference between credit and debit for a checking account when i purchase something?

when im paying for something at a store, is there a difference if i pay with debit or credit.i have a checking account for bank of america. i know i worded this question badly. but any input appreciated.thanks!|||My bank charges me 50 cents if I use it as a debit, so I use it as credit, ask your bank if the fees are different.|||they both come out of your checking account. with debit the money comes out right when you put in your pin number and with credit it takes about 2 days and you sign.|||I have an account with a different bank but I can use my bank card as either a debit or credit card. Both options take the money immediately from my bank account. When I use debit I have the option to withdrawal funds from my account. For debit I must enter my pin. For credit I must sign my name. For credit I get special rewards. I personally use my card as a credit 95% of the time because I feel it's safer for me to have to sign my name than use a pin where someone can observe what that number is.