The problem description is as follows:
Novice Xiao Bai. Ask for advice
There are two branches related to master locally, one is called master and the other is called origin/master.
Every time you pass git fetch, you will update all the origin/xx to the latest (synchronized with the remote), so if there are any branches on the git server, there will be an additional origin/xx after the local git fetch.
These two may not be synchronized, for example, you have written several commit on master, so master will be ahead of origin/master. Some commit have no branch name, which means that the HEAD pointer of no branch currently points to this commit.