Branching is too helpfull for a development. If some of your coworker has pushed a his local branch to remote branch and you want to make some changes to it you can do it by checkout.
To check out his/her branch on your local machine you need to follow these
git fetch origin
Where origin is a remote server. Now when you will do
git branch -r you can see all the branches which has been pushed to remote.
git checkout -b test origin/test
Above command will checkout test branch from
origin remote and will create test branch in your local branch.
Now you can commit and push to the remote branch.