The primary use for TFS is for event planning, including things like writing the user story and then assigning tasks to the developers. Another task is writing test cases, then recording test results, and sending bugs to the team members. The third thing is that we use TFS as part of our CICD pipeline.
As part of our pipeline, we use it for checking in code and it acts as a repository. This leads to the fourth thing we use it for, which is to move the code from dev to QA to production. Essentially, we establish a complete lifecycle using TFS.
We also use it in conjunction with Azure DevOps.