An SLA is defined as a documented agreement between a service provider and a customer that identifies both services required and the expected level of service.
SLAs are used to measure the performance of services from the customer's point of view, and it is important that they are agreed in the wider business context.
Some of the key requirements for successful SLAs include:
They must be related to a defined 'service' in the service catalogue. Individual metrics without a specified service context are unhelpful.
They should relate to defined outcomes and not simply operational metrics. This can be achieved with balanced bundles of metrics, such as customer satisfaction and key business outcomes.
They should reflect an 'agreement': an engagement and discussion between the service provider and the service consumer. It is important to involve all stakeholders, including partners, sponsors, users, and customers.
They must be simply written and easy to understand and use for all parties.
https://www.bmc.com/blogs/itil-service-level-management/#:~:text=Service%20Level%20Agreements%20(SLAs)&text=Some%20of%20the%20key%20requirements,and%20not%20simply%20operational%20metrics.

The ITIL SVS describes how all the components and activities of the organization work together as a system to enable value creation.
The SVS is made up of specific inputs, elements, and outputs relevant to service management. The key inputs to the SVS are opportunity and demand. The output of the SVS is value delivered by products and services.
Opportunity refers to options or possibilities to add value for stakeholders or otherwise improve the organization.
Demand refers to need or desire for products and services among internal and external consumers.
https://www.bmc.com/blogs/itil-service-value-system/