You branched off from develop, but develop has moved forward. How do you update your branch to the current state of develop? What is rebase?

If you have created a branch from develop, and new commits have appeared in develop, to update your branch, you can perform a rebase:

git fetch origin
git rebase origin/develop

This will move your local commits on top of the current state of the develop branch, maintaining a linear history. Rebase is an operation that "rewrites" the history of your branch by applying your changes on top of another base (in this case — the updated develop). It helps avoid unnecessary merge commits and keeps the history clean.

Important: after a rebase, if the branch has already been published, you need to push with the --force or --force-with-lease flag to overwrite the history on the remote repository.