Delegation

You can delegate your tokens by submitting an escrow transaction that deposits a specific number of tokens into someone else’s escrow account (as opposed to staking tokens, which usually refers to depositing tokens into your own escrow account).

In other words, delegating your tokens is equivalent to staking your tokens in someone else's validator node. Delegating your tokens can give you the opportunity to participate in the Casper Network's proof-of-stake consensus system and earn rewards via someone else's validator node.