mSOL is a liquid staking token you receive when you stake SOL on the Marinade protocol. These mSOL tokens represent your staked SOL tokens.

They act as a receipt, allowing you to exchange them later on for your staked SOL and the earned rewards. Meanwhile, you can use mSOL in DeFi while enjoying your staking rewards.

If you're planning to hold your $SOL tokens long-term, it makes sense to earn yield while doing so. Staking the $SOL tokens would be the best approach, but it requires your tokens to be locked for a certain period.

You can check out their X handle or their whitepaper to read up.

X: @marinadefinance