All contracts or services managers should know those terms. Basically this is a way to simplify contracts terms regarding what the service provider should deliver by quantifying in a more operational language.
One of the most common forms of SLA (at least in my current area) is service availability: how long a network link or a server stay up and running or how quickly the service should be used restored in case of disruption.
In case of SLA breach it can be ask financial compensations.
I do deal a lot with SLAs in my job. Not only with 3rd party external providers but also with my internal clients: we are all service provider of someone at the end of the day anyway 🙂
However I realized that we are signing of on SLAs without really understanding the field reality. Good SLAs should be achievable otherwise it is like selling a dream to the customer. I regularly hear people saying: « we signed off on such SLA so we are covered ».
Well the only cover party here is the service provider who just signed a golden 5 year contract. And Guess what, when the service disruption happens, your management won’t blame the 3rd party but you since you are the local person.
So you need to make sure you understand what make sense or not, what is feasible or not, and most importantly what may happen and how often.
Indeed SLAs are based around probabilities which are based on past history.
Then the service provider will implement mitigations plan in case of failure in order to keep Service level green. As a SLA customer you need to know such history as well.