From experience in working with TFS for this year, i can say that When you check in your changes, they are stored on the server as a changeset. Changesets contain the history of each item in version control.
You can view a changeset to get information about:
>which files were changed
>what the exact changes were
>who changed the files
>what the check-in comment contains
>which work items are associated with the changeset
For more info on how TFS works when checking in code and handling changesets, click