Not sure your starting point, but:

Where sats are stored on the blockchain and your keys let you spend (you don’t carry your sats around), ecash tokens are like a physical “check.” It’s an IOU from an ecash mint that probably has a lightning node attached to it.

If the lightning node and mint stay solvent, you will be able to redeem your IOU for sats, or whatever the IOU is for. (Some use USD)