What happens inside the Git system when executing the merge command to combine branches?

When executing the git merge command, Git attempts to combine changes from one branch into another. The process includes:

1. Finding the common ancestor of the two branches.
2. Comparing changes in each branch relative to the common ancestor.
3. Automatically merging changes if they do not conflict.
4. If there are conflicts (the same lines changed in both branches), Git marks them for manual resolution.
5. Creating a new merge commit that combines the history of both branches.

Thus, merge preserves the change history and combines code, allowing multiple developers to work in parallel.