Pools allow token holders to 'stake' their tokens into a pool in order to receive rewards. Rewards are scaled based on the amount of tokens a holder has committed relative to the overall amount of tokens staked across the ecosystem for that pool. Rewards are emitted based on the epoch or time designation.
Typically, Pools have an expiration date however the CroSwap $CROS pool has no expiration date as it is directly tied to the $CROS emitter. Pools with an expiration date are short-term promotions designed to introduce new projects.