A Repository Trigger is used to trigger a Configuration when a change is committed to a certain repository.
Trigger Options
Quiet Period
When a change set is detected on the selected repository, a build is created and put in the Build Queued state. It sits in the queued state until the quiet period expires. While in the quiet period, additional commits to the repository won't trigger new builds but instead append those change sets to the build that's in the quiet period. This is useful when you want to group a set of quickly commited changes into one build.
Distributed Version Control System (DVCS) Options
The options for a Repository Trigger differ slightly depending on the type of repository you select from the drop down. If it's a distributed version control system (DVCS), you will get additional options such as which branches will trigger a build.
For example, you could setup a repository to monitor all branches then create a different repository trigger for each type of branch... dev branch, release branch and/or feature branches.
The three types of branch monitoring options are:
All Branches
When this option is selected, the trigger will start a build if any changes are made to any branch. You also get the option to only send notifications to users who triggered the build.
Default Branch
When this option is selected, the trigger will start a build if a change was made to the repositories' default branch. The default branch is specified when you create a repository.
Pattern matched branch
When this option is selected, the trigger will start a build when a change is made to a branch whose name matches the regular expression you supply. You also get the option to only send notifications to users who triggered the build.
The regular expression entered in the screen shot above is ^f-.*. This will match any branch in your repository that starts with f-.