The house edge is a mathematical advantage the casino has over the player in a game of chance. Casinos have a legal right to set the house edge in its games and, in sum, this translates into the company’s profits to pay large staffs and other commodities for the customer.
The house edge derives from probability, so any hand dealt, dice roll, or roulette spin is still unpredictable.
House edge is also expressed as a percentage. The percentage indicates how much a player expects to earn on payouts when a player theoretically bets $100. So, if the house edge is of 1 %, that means the player must expect to lose $1.
Even though the casino has a probabilistic advantage, we are dealing with odds, not certainties. Variation happens in the course of any casino game. Variation is how much the results differ from expectations.
The variation means that sometimes you will win more than 100% of what you bet (and thus you have a winning session) and sometimes you will lose more than you expected to lose.