Staking is an easy way to earn passive income and support the stability of the network without any need to lock up the tokens or lose them in any way.
As described in the What is Cardano section, the stake pools probability to be selected to produce a block depends on the amount of ADA that is staked with it. The more stake is delegated to a stake pool (up to a saturation point), the more likely it is to make the next block and earn the rewards that are shared between everyone who delegated their stake to the stake pool.
Once a pool reaches the point of saturation it will offer diminishing rewards. (The goals of saturation is to prevent centralization by encouraging delegators to delegate to different stake pools and to prevent single pools from becoming to large.)
Every ADA holder should stake ADA. There is no risk of losing the coins as those never leave your wallet while the process of staking helps the decentralization of the network. Staking ADA is comparable to giving voting power where the power equals the amount of coins in your wallet, but the coins never leave the wallet and can be freely moved around.