An initial branch is automatically created when you add a new repository in a database. This is especially true for the initial repository automatically added when you create a new database. Any set of changes to items — that is, model, files, and tags — are saved in commits on this branch. See Basic Version Control for more details.

You may think of a branch as a sequence, or history, of such commits. Each commit identifies a collection of versions that were the most recently saved, or latest, at the time of the commit. Any particular version could have been saved in that particular commit, or in a previous commit. Each commit also identifies the tag assignments to items at the time of the commit. By comparing the collections of item versions, as well as the assigned tags of items, present in two different commits, Model Manager can infer all item changes done in-between the first commit and the second commit. See Figure 2-2 for a schematic representation of a branch containing three commits.