What is the difference between deactivating and uninstalling

When you deactivate a plugin, it only gets disabled from your site. But it remains installed on your site. You can activate it again later. You can check Deactivate plugin by going to Plugins >> Installed Plugin >> Inactive plugin page.

But when you uninstall a plugin from your site, it gets completely removed from your site. If you want to use that uninstalled plugin again on your site, you will have to reinstall it.