What do “trunk” and “branch” mean?
The trunk is where most Mozilla development happens. Because it is under constant development, there are often regressions. Before each release, a branch is created from the trunk. This allows heavy development to continue on the trunk while the branch takes fewer changes (mostly changes that improve stability and fix regressions). As a release nears, its branch takes fewer patches, and those patches are checked carefully to ensure they do not decrease stability. Some branches, such as the Aviary branch that produced Firefox 1.0, exist for months and take large patches. This is rare. When a branch is active, there are usually nightly builds available for both the trunk and the branch.
