A payout is the amount returned to a player when a bet wins, or the act of paying withdrawn funds to a player account.
The word appears in game rules and in banking messages with two different meanings, which is a common source of confusion in support chats.
A 10 euro bet at decimal odds of 2.50 has a payout of 25 euro, made up of 15 euro profit plus the 10 euro stake returned.
At decimal odds, yes. The payout figure is stake multiplied by the odds, so it contains the returned stake plus the profit.
Payment teams use payout for money sent out of the account. It refers to the transfer, not to a winning bet.