In WordPress, custom fields is a special feature that allows authors to include additional information when writing a post. This is sometimes known as “post meta” because WordPress stores this information as metadata that is coded according to the template’s tags.
Another way to think about custom fields is that they are an additional way to create a new taxonomy by using special tags to a post, just in a different way than the standard tags.
For example, you could create a custom field called “How I’m feeling right now…” and then each individual post would be “tagged” by the emotional information that you input in this custom field. Later, you could sort your posts by the responses given to the custom field of “How I’m feeling right now…” in order to track your emotional state over time or group posts by emotion.
By default, custom fields are hidden. To see them, click on “Screen Options” at the top of your screen and then activate “Custom Fields” when creating a new post. You will then see the custom field immediately beneath the post edit section.
Note: Whether or not you can use custom fields depends on the version of WordPress you’re using.
Certain themes and plugins come built-in with special custom fields. For example, including metadata for each post for SEO purposes would be an application of custom fields in WordPress.