The main image associated with a page or article, often used in previews and content listings.
A featured image is an image assigned to represent a page or article in a publishing system. In WordPress it is also known as a post thumbnail. A theme or template can use that association in listings, article layouts or other places where it needs a representative image.
Assigning the image and displaying it are different actions. A template may show it at the top of an article, use it only on archive cards or not display it in a particular view. Social-preview metadata may also be configured separately, so selecting a featured image does not prove every shared link will use it.
Choose an image that accurately represents the content and remains understandable when cropped in different contexts. An unrelated stock image may fill the space without helping a reader recognize the subject. A photograph containing important text can also lose that information when displayed as a small card.
Takeaway: Select a relevant representative image, then check where the site actually uses it. Review article, listing and social-preview behavior separately instead of assuming one CMS field controls all three.
Example
A design studio assigns a wide project photograph to an article. It looks effective on the article page, but the archive card crops out the finished work. The editor should check the template’s crop and choose a suitable image or focal point rather than assume that the full original will always be visible.
What to check
Confirm permission to use the image, provide an appropriate text alternative where it is displayed, and use a suitable file size and format. Keep any independently configured share image consistent with the article, without claiming that image selection alone improves rankings.
For more detail, see Featured images and post thumbnails.