I've updated a bunch of modules in my local development environment and then committed the code changes using git.

On my test site, I've pulled the code and ran drush updb but it's showing that nothing needs to be updated and that the modules I updated are now current. In the past, every time I've performed updates, I was under the assumption that there was a database updating component to it and whenever I ran drush updb it would take the code that was just implemented with git and run the update. Not sure, why it's different this time, can someone explain? Am I missing a command?

If database updates aren't require for all module updates, can someone explain why?