How are SLAs related to Internal Tickets?

A Service Level Agreement (SLA) is a contract between a service provider and an end-user that defines the standard of service expected from the service provider. In the case of internal tickets, the service provider may be any department or person with whom you have raised an issue. 

For example, the internal SLA policy in an organization may state that infrastructure-related issues must be resolved within one week and pay-related issues within two days.