In a nutshell :
-> Git Merge: It will simply merge your local changes and remote changes, and that will create another commit history record
-> Git Rebase: It will put your changes above all new remote changes, and rewrite commit history, so your commit history will be much cleaner than git merge. Rebase is a destructive operation. That means, if you do not apply it correctly, you could lose committed work and/or break the consistency of other developer's repositories.