Volatility measures how widely results scatter around the average return. A game rated low pays modest amounts at a steady pace, and a game rated high concentrates its return in rare, large wins, often inside a bonus feature. Studios describe it on scales of three or five levels, sometimes with lightning bolts or bars instead of numbers, and the scales are not comparable between studios. Choosing a level is a matter of taste and budget, while the cost over the long run stays put.
Hit frequency is the share of spins that return any win at all, and games often publish it in their help pages. A figure of one in four means that, on average, three spins out of four pay nothing. Many of the wins counted are smaller than the stake, so a hit does not always mean profit on that spin. A high hit rate keeps a balance moving slowly, while a low one lets it fall in bigger steps between payouts.
Measured returns drift away from the theoretical figure over any stretch a person can play, and the gap narrows only across millions of spins. Tracking sites that pool results from many players show this clearly: a game can run far above or below its figure for weeks. Demo modes normally use the same maths as real play, so a free session shows the rhythm of a game, although a short demo run says as little about the true return as a short paid one.