The icons to the left of the branch name represent the differences between your working copy and the local branch your working copy is checked out from.
A green checkmark means there are no differences. The two icons above refer to "files changed" (90) and "unstaged new files" (1). There is also a green icon for staged new files, grey or red minus icon for deleted icons (staged or unstaged), a yellow exclamation for conflicts, and a yellow arrow for renamed files. There may be some other less common potential differences that I've never seen as well.
There are also green arrows that can show up to the right of the branch name the represent how many commits are waiting to be pushed (up) and/or pulled (down) from remotes.
EDIT: The branch icon means that the name next to it is a branch. If it has a check, that's the branch that is checked out.
Supported Platforms macOS Sourcetree has a lot to offer and, like many developer tools, finding and using it all can be a challenge, especially for a new user. Everyone might not love ...
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