The database. This is where all the records of the items, the elements, texts, most configuration, is stored, and it’s covered by your .sql file;
The uploaded files. On a standard site, these are just in the “files” folder, so they’re included in your tarball/zip of the Omeka folder;
The Omeka application files. This is the Omeka software itself plus your plugins/themes/etc. plus certain pieces of configuration. Your tarball/zip of the Omeka folder will also include this.
For totally standard sites where you’ve made no changes to any code and you’re using stock themes, plugins, etc., just the first two can be sufficient as a backup, because you can just get new copies of Omeka and your plugins and themes. But what you’re doing, including everything, is a good idea regardless; it makes it simpler to do faster restorations, and it makes sure you’ll capture configurations and any possible customizations to files you may have made.