A Service Portal is a system that allows a Team to produce services that are requestable by others. They can add information about the service and add questions specific to their request(s).
A service is a function/requestable item that a team provides to others. It includes a description, and a form to collect details needed to fulfill a request of the service (which is called a Request), and a fulfillment process that allows for fulfillment of the service.
A request is a service usually submitted by a user that has a fulfillment process and a request lifecycle (Typically: Draft -> In Progress -> Closed / Cancelled).
A fulfillment process is an ordered set of tasks needed to fulfill a request.
A task is a step in a fulfillment process that is completed by a team member.
A team is a collection of users.
A Discussion is a conversation about a topic like a request, task, or team.