Hello @Alex! Welcome to our community. I hope, you like it here.
You should definitely check out:
Meanwhile, let’s try to clear things up:
When you update, you will get newer versions (e.g. bugfixes, sometimes added features) of your installed programs. This should be done regularly.
An upgrade is something more profound. It will turn your operating system into a new one. System settings will possibly change, new libraries and applications will be installed, obsolete stuff removed.
You should never do it before making a backup of your system!
Your distribution’s homepage should have detailed guides about how to perform version upgrades.
There is also a tutorial at ItsFoss