Working with Version Control Changesets
A changeset is a logical container in which Team Foundation stores everything related to a single check-in operation, specifically: file and folder revisions, links to related work items, check-in notes, a comment, policy compliance and system metadata such as owner name and date/time of check in.
When you check in a set of pending changes, Team Foundation creates a new changeset in the source control server and assigns it a unique changeset number. Changeset numbers increase sequentially. For example, changeset #3 precedes changeset #4, and so on. No two changesets may have the same date/time of check in. Because of this property, changesets also represent particular points in time for the state of the server.