The pie chart shows which liquidity gauge receive the most CRV.
Just because a pool has a larger weight doesn't mean it will have a higher APY. The CRV allocated to a gauge is shared between all the liquidity providers in it.
Why are gauge weights so important?
Because those weights decide where the CRV inflation goes, it allows the DAO to control where most of the liquidity should go and balance liquidity. It's a powerful tool for voters that must be used responsibly.
Currently, gauge weights are updated once a week on Thursdays around midnight UTC.