The term net winnings can apply to any type of gambling actively and it is used to describe the amount of cash that you have won when you have placed any type of winning bet.
Be aware that when you place a bet you will be paid back your winning payout and that payout will include the original stake you wagered on that bet. So for example if you place a bet on a horse and it wins at odds of 2 to 1 and you staked 100.00 on that bet then your total winning payout will be 300.00.
However, the net winnings on that bet is 200.00 as the additional 100.00 you will received as part of your winning payout is the original stake your placed on that wager.
So when you are working out your net winnings on any one single bet or wager you have placed or on a series of winning bets you must always deduct the original stake you placed on those wagers to arrive at the correct net winnings figure.