What is staking and delegation on Cardano?

Every ada holder owns a stake that is based on the amount of ada they have. A developer or a tech-savvy person can set up a stake pool and run it to help verify Cardano transactions and create new blocks getting rewards for this. Everyone can delegate their funds to a stake pool to earn a share of these rewards. There is no risk to this and no ada leaves your wallet. Ada can be delegated from your wallet or spent at any time.