How many times the below thing happens to you?
  1. You have created 
    hotfix
    or patch branch in your work
  2. You have pushed your commits to your work remote repo
  3. There has been a update in master leaving your 
    hotfix
    branch out-of-sync with master.
  4. You will be forced to "Sync them"
  5. Now is the question? 
    git rebase
    or 
    git merge
    ?
Though, 
git rebase
is the keyword everyone uses and your managers will force you to rebase without knowing consequences.
Simply, 
git rebase
won't work. Will explain you why.
git rebase
takes all the commits from your 
hotfix
branch and applies on the new branch out of master as if that 
hotfix
commit was never made.
It is like as if yourself
  1. Takes all the changes in the first commit of 
    hotfix
    branch and then applies the changes to the corresponding files manually via a code editor and then you commit them like usual in a new 
    temp
    branch cut out of master.
  2. You would repeat 1 for all the commits in your 
    hotfix
    branch.
  3. And then you would delete the old 
    hotfix
    branch and rename the 
    temp
    branch as your 
    hotfix
    branch
git rebase
automates the above steps with optimisations. You can read about 
git rebase
in here.
One thing you might have noticed that the old 
hotfix
branch and new rebased 
hotfix
branch are not the same, though their contents are. you can confirm them by 
git log
. You will see the new datetimes and new hashids or commit ids compared to what you saw in the old 
hotfix
.
So, now when you try to push the changes to 
hotfix
branch, you will get an error similar to, "Updates were rejected because the tip of your current branch is behind its remote".
This is completely understandable since both branches have different ids in their history and no commit in common except for the base commit out of master.
And a normal 
git push origin hotfix
cannot force the remote repo to override its 
hotfix
branch.
Most often, Your organization would have disabled 
force-push
, which lets u overwrite the 
hotfix
branch.
Only working option u have is 
git merge
.
git merge
is a very simple command. It adds a merge commit on top of current 
hotfix
in addition to resolving any conflicts. You can read about it in here.
Now, you can easily push the branch because you are pushing only a single commit on top of existing 
hotfix
branch without changing old commit ids.
So local 
hotfix
is same as remote 
hotfix
but one additional commit in local 
hotfix
. But both 
hotfixes
share the same history except for that one additional commit. Thereby, Remote can fast-forward its remote branch.
TLDR; don't use 
git rebase
, if u have pushed your branch to remote. Always use 
git merge
.