No-deposit bonus
A small amount of bonus money or free spins granted without a deposit, usually under tight conditions.
With a no-deposit bonus, you get a little bonus cash or some free spins just for registering, confirming your email or redeeming a code. No deposit is required to claim it.
Free to try, hard to cash
It lets you look around a casino at no cost, but no other bonus carries harsher terms: steep wagering, a brief expiry, a low max cashout and a list of games you cannot play. Many sites insist on a deposit before the first withdrawal, even of no-deposit winnings, and most will want KYC.
Example
You receive 20 free spins worth $0.20 each and win $8. That $8 becomes bonus money under 50x wagering ($400 in bets) with a $50 cap. Clear it, and you still have to deposit $20 before a withdrawal goes through.
Best use
Treat it as a way to try the lobby, the games and the support desk. It is a bad way to judge withdrawals, because the added conditions tell you little about how real cashouts are processed.