RTP describes the amount a slot will pay back to a player over many spins and is usually expressed as a percentage. For instance, a slot with an RTP of 98% will give about $98 for every $100 that goes into it. So, the online casino can expect to profit by 2% from this particular slot over some time in use.
What’s important to understand is that this number is based on millions of spins, so it comes down to being in the right place at the right time. What makes slots exciting is that nobody knows when specific slots are primed to pay accumulated excesses of funds.