Polkadot is a network protocol that allows arbitrary data—not just tokens—to be transferred across blockchains. This means Polkadot is a true multi-chain application environment where things like cross-chain registries and cross-chain computation are possible. Polkadot can transfer this data across public, open, permissionless blockchains as well as private, permissioned blockchains.
Delegators in Polkadot are called Nominators. Anyone can nominate up to 16 validators, who share rewards if they are elected into the active validators set.
Simply choose 1-16 validators (staking providers) who you trust and nominate them. If more than 256 nominators nominate the same validator, it is "oversubscribed", and only the top 256 staked nominators (ranked by the amount of stake) are paid rewards. In other words, if a validator is oversubscribed and your stake is in place 257 or higher, you will not receive staking rewards.
Please note that you must manually claim your rewards using the function inside the staking tab. Staking rewards are kept available for 84 days only. If you do not claim your staking rewards by this time, then you will not be able to claim them and some of your staking rewards will be lost.
Please note that there is an unbonding period, which serves as a cooldown. You will be able to transfer your tokens after this time has passed (28 days on Polkadot). After 28 days of unbonding, the DOT will be in the "Redeemable" state. At this time, the unbond DOT can be redeem by using the redeem function. Please note that during the unbonding period, you will not receive any staking rewards.