When DeFi protocols discuss staking, they usually refer to the process by which you can temporarily lock up your tokens in exchange for a protocol-specific reward.
You will receive your locked tokens back upon unstaking. There is also a timelock upon unstaking (one week for SRM).
SRM staking rewards come from DEX trading fees. One part of the fees will go towards buy and burn, and the other part will go towards staking rewards dropped onto all stakers.
Staking rewards are an equal mix of locked and unlocked SRM.
Having the staking process all on-chain is the difference between a self-sustaining decentralized protocol and leaving the process to trusted central party.
Builders can create their own GUI's and to check out Serum's developer resources.