Paid is the past tense of the verb "to pay" meaning to give money
I paid the restaurant bill with my credit card.
"To pay out" means to give money out
The bookie will pay out 5 to 1 on the game tomorrow.
"To pay off" means to pay a debit in full; to bribe
I finally paid off my car loan.
He paid off the referee so his team can win the game.
Pay out and pay off are phrasal verbs. For example "pay" + "out" must be used together to get the correct meaning.