A service level agreement (SLA) is like a promise between two people. It's a promise that one person will give the other person something they need, like a toy, candy or a ride to the park.
In the same way, companies often make promises to their customers in the form of an SLA. The company promises to give the customer a certain level of service, like fast internet or always available customer service.
The SLA also includes details about what will happen if the company doesn't keep their promise. For example, if the internet is slow for too long, the company might give the customer a discount or a refund.
The SLA helps make sure that everyone knows what to expect and that the company takes responsibility for meeting those expectations.