Staking service providers are responsible for running the Elrond Network validator nodes. This will keep the network secure for everyone and earn you new eGold in the process.
In exchange for this service, staking service providers take a commission on all rewards generated. In other words, they only make money when you make money.
Staking Providers can decide to set any service fee they want. The Elrond Foundation nodes service fee is: 10% and it is applied as a percentage to the earned rewards.