If you have chosen an open-source WordPress theme for your new WordPress blog, it’s a good idea to create a “child theme” based on the template you have chosen, so that when you update your WordPress version, your theme will remain intact — otherwise, whenever you update your WordPress blog (and updates to WordPress are happening all the time!), your style sheet and php files will be replaced by that particular WordPress theme defaults.
Commonly referred to as a child theme, your new WordPress template will be based on the changes that you made to the original WordPress theme that you chose when you developed your WordPress blog.
WordPress.org provides documentation on how a child theme works and what you can do to set up your own WordPress child theme.
Whenever you update your WordPress release, it is highly recommended that you back up all of your WordPress files, including your child theme, as well as the database you have created for your WordPress blog. WordPress blogs commonly use MySQL databases — consult your hosting provider on how to download and backup your database.
Consider creating backups on multiple drives or use a file-saving vendor — you can also backup your files onto disks and store the disk(s) in a safe deposit box.
