Staking
Staking is locking up coins to help secure a Proof of Stake network in exchange for rewards.
In depth
You can run your own validator (which needs technical setup and a minimum deposit) or delegate to one and share its rewards. Rewards typically come from new issuance and fees, expressed as an annual percentage. Risks include lock-up periods, validator penalties and the price of the coin itself falling.
Why it matters
Staking is the mechanism behind "earn" products; knowing where the yield comes from helps you judge if it is sustainable.