As described in the Uniswap V3 Liquidity section, liquidity positions must provide liquidity that is in-range relative to the current price so that the protocol isn't distributing TCP for liquidity that is not useful. In order to incentivize people not to add liquidity that is out of range, the community can liquidate out-of-range positions and keep a portion of the proceeds.
Liquidity Position Liquidations (this page)