Solana (SOL) Staking Basics
To take part in the Delegated Proof of Stake process, users delegate SOL to validators. Validators are the infrastructure operators on the Solana network. The process of delegating SOL to a validator is called staking.
By staking, you take part in the consensus mechanism, while also receiving inflationary rewards. Read in-detail.

Is staking safe?

Assigning your tokens to add to a validator’s or stake pool’s stake-weight is known as “delegating” your tokens. Delegating your tokens does NOT give the validator/stake pool ownership or control over your tokens. At all times, you still control all your staked tokens that you may have chosen to delegate.
When it comes to stake pools, some of them (like Eversol) use the standard Solana Network Stake Pool Program – "a program for pooling together SOL to be staked by an off-chain agent running a Delegation Bot which redistributes the stakes across the network and tries to maximize censorship resistance and rewards". This program has been audited by multiple security firms to ensure the total safety of funds.
Some stake pools might use a customized contract or have built their own. Various pools have different delegation strategies and their rewards distribution varies.
Hence, you should always do your own research and trust stake pools that are transparent enough. Check out the pool stats, and security audit information, research the team behind the business and their contacts and check if they have any other blockchain-related products.

What is a Solana stake pool?

"Stake pools are an alternative method of earning staking rewards. This on-chain program pools together SOL to be staked by a staker, allowing SOL holders to stake and earn rewards without managing stakes." Read more.
Despite the fact that users can independently delegate their stake to a single validator, there is currently no simple solution that helps users easily distribute their stake among several validators.
A stake pool helps users accomplish this goal, while also supporting network decentralization. Stake pools allow users to distribute their stake across many validators. Each stake pool has its own unique criteria for delegating to different validators, known as "delegation criteria".

Why does depositing into stake pools help decentralization?

"Stake pools can help decentralize the network by allowing for an easier way to delegate stake across many validator nodes. Assuming the chosen delegation strategies by stake pool managers favor an even distribution of stake, the delegation across many validator nodes will reduce the concentration of stake on any given validator node, and in turn, reduce the likelihood of a halting event.
Stake pools can also be seen as insurance against any single validator’s downtime that may arise from performance or other issues." Source.