WordPress stores your theme files in /wp-content/themes/ folder. You can edit a theme file, but it is generally not recommended. As soon as you update your theme to a newer version, your changes will be overwritten during the update.
In many WordPress 教程, you will see code snippets that you can add to your WordPress site. The best way to add custom code to your WordPress site is by adding it to 函数.php file of your child theme or by creating a 特定于站点的插件.
WordPress stores all your image and media uploads in the /wp-content/uploads/ folder. By default, uploads are organized in /year/month/ folders. Whenever you are creating a WordPress backup, you should include uploads folder.