In-play betting involves betting while an event is in progress. At the start of selected events, unmatched bets are cancelled and an in-play market is opened. This allows you to bet right up until the final whistle of a match, the final game of a tournament or the winning post of a race.
These events are clearly indicated by this in-play “tick” icon at the top of the market view.

Specific rules apply to in-play markets, depending on the sport. These relate to certain circumstances in which markets are suspended, where unmatched offers are cancelled and the market restarted, and to delays applied to bets in order to protect against minor delays in broadcasts.