It is a feature that allows players to withdraw their bets before the end of the event. As mentioned, early cash-out betting is a way to end the bet before the sports competition ends, allowing you to make a profit before things potentially go wrong or to stop the bleeding before things get out of hand. It is not a valid option for all bets on all sportsbooks, but it is becoming widely available and popular based on apparently growing demand.
Cashing out early is a way for sports bettors to protect themselves against unpredictable turns in the course of games or matches. When you cash in early, the rest of the match becomes irrelevant. The only thing that matters is the position of one's bet when one decides to cash out.
In this way, bettors can guarantee themselves a profit when they are ahead or potentially recoup some of their wager to minimize their losses if they are at a disadvantage. An early cashout will never be for the full amount of the bet, which reduces the potential winnings but also ensures that the entire stake is not lost.