When traders can't execute during the session due to lack of liquidity, they place market-on-close orders that execute at the bell. The imbalance between buy and sell MOC orders can drive big price swings at the close.
See, they totally hunted for liquidity. That's what we call the market on closing balance. At the end of each session. Market participants that were not able to place their orders inside of the session due to lack of liquidity, they're going to put it at the end of each session with so called market on close orders. And the imbalance between buy and sell orders is called the MOC imbalance. It creates this huge market movement at the end of each session. Okay, okay.
