Go to Tools>Export. This will create an XML file of all your posts, pages, comments, etc for you to download. That’s typically all you have to do.
Whenever you need to restore your site just go to Tools>Import and upload the XML file.
You can also check out the WP-DB-Backup plugin – https://www.ads-software.com/extend/plugins/wp-db-backup/ I’ve never used it but it has 4 stars and over 100 ratings. This plugin will save all the data from the core WordPress database tables. To restore the database you’ll have to use phpMyAdmin (rather than WordPress itself) which might be complicated if you’re new to databases.
You might also look into doing full site backups. If that’s what you want to do, you should check out your host’s website for more information.