Say you create a new branch from a head to work some enhancements, and simultaneously some bug fixes were made on the trunk. Suppose that a month has passed since you started working on your new branch and your new feature are not finished yet, but at the same time you know that other people on your team continue to make important bug fixes on the trunk. It's in your best interest to replicate those changes to your own branch, just to make sure that they integrate well with your changes. This is done by performing a sync merge, which is a merge operation designed to bring your branch up to date with any changes made to its ancestral parent, which is the trunk in this case. The sync merge is also known as rebasing.
