From one of most followed blogs, When you do git fetch, Git gathers any commits from the target branch that do not exist in your current branch and stores them in your local repo. However, it does not merge them with your current branch.
After fetching all the commits, where does git store all these commits (since, it's not merging them with my local branch) and how does git repo history changes when i do git fetch?
It stores them in exactly the same way as it stores any other commit.
Git commits are not stored in a branch; rather, a branch is just a pointer to a specific commit.