A branch is *the* Git element that allows to make modifications to a project in "isolation", aka without any risk of breaking anything in the project. The main use of branches in development projects are to dedicate a separate branch to each of a program's feature or functionality. And to merge the branch back into the main project branch once the feature has been implemented and tested. Branching also makes sense for single-person projects, when several, preferrably unrelated, parts of the project can be worked on at the same time. When one of the parts is finished it can again be merged into the main project branch. Branches are also useful when some experimentation is needed (ex. : exploring a new implementation of an algorithm in a development project, writing alternative closing chapters for a book managed by Git). If the experimentation is not successfull, the branch will never be merged into the main branch, and can be deleted altogether (remember, it will still be in the project's history anyway).
### Important notes
1. When creating a repository, Git always creates a `main` branch (sometimes called `master`), and makes it the default branch when cloning the repository.
1. It is a bad practice on a collaborative project to create a branch per contributor. Contributors can work on several aspects of a project, and multiple contributors can work on the same set of files. Using one branch per contributor will quickly lead to merging nightmares.
## Using GitLab to manage branches
The GitLab UI provides all the functionalities to manage branches. Until now, we always used the `main` branch. The following screencast shows how to create a branch in GitLab. When creating a branch, it is recommended to use a meaningful name.The branch will be dedicated to complete information about imaginary animals. By creating this branch, imaginary animal experts can happily work on their favourite pets with the assurance that they will not thread on other domain expert's toes (even if imaginary animal experts can step on each other's toes, more on that later.)
Working on the project's content in a specific branch is no different from working on its contents in the main branch: adding, editing, renaming or removing files behave as usual. Except that the modifications are contained to the branch and not visible in other branches. As can be seen in the following screencast: contents are added with the GitLab UI in the `imaginary-animals` branch, but when switching to the `main` branch they are not present.
