All site content for your WordPress site is stored in the database. The files that query and display the data, store settings, etc, are in the theme and plugin folders. There is the wp-config.php file that stores access credentials for your database. And media files are stored in the wp-content folder, but media files locations are stored in the database.
If you have a backup of your database, you can essentially recreate all content by installing the latest versions of themes and plugin, then activate as required. You also need a backup of your media file folders and files. With those items, you can essentially recreate your site.
That means that it is important to not only backup your database, but also your media files. There are plugins that will allow a re-sync of media files into the database, but a backup of everything (database, themes, plugins, media folders and contents) is an important thing to do – that will help you recover from problems.
Your hosting company may do backups of your entire public_html folder, and your databases, so you could contact them to restore all or part of your site. But a backup plugin that takes care of all databases, and the folders/files in themes/plugins/media is a good thing to have – especially if those backups are stored ‘off-site’ (for instance, emailed to you).