What happens when create new brand in Git?

Question

I'm new to Git and SourceTree tool. I don't understand why this happens?

My steps:
1. Create new brand, named develop/john/LinksMiddleware/new
2. Stages changed files, for more details there're three files.
3. Commit

=> Expected: In new brand only contains three staged files in step 2th above
=> Real result: In new brand contains all source code files as in my local working directory.

Answer 1

When you create a branch then you get something like a copy of original branch. So when you are on master branch and do git checkout -b "myNewBranch" then you will have 2 identical copies of your code. You can add changes to them and then merge those changes.