Turnover has several distinct meanings:

1. In sports, a turnover happens when one team loses possession of the ball to the other team, often by mistake. In basketball, if you throw a bad pass that the other team catches, that's a turnover. In football, fumbles and interceptions are turnovers. Teams practice hard to avoid turnovers because each one is a wasted opportunity and gives the opponent a chance to score.
2. In business, turnover refers to how quickly something gets replaced or cycles through. Employee turnover means how often workers leave and new ones get hired. A store with high inventory turnover sells its products quickly and restocks often, like a busy ice cream shop that runs through its inventory faster than a furniture store. Turnover (common in British English) can also mean the total amount of money a business brings in.
3. A turnover is also a type of pastry: a pocket of dough folded over a sweet or savory filling, like an apple turnover. The dough gets turned over the filling, which explains the name.

The key idea connecting these meanings is something changing hands or cycling through: possession of a ball, employees at a company, products on a shelf, or dough folding over filling.