How to Use the WordPress Featured Image Feature (Indonesian Version: Gambar Unggulan) – Its function is to add featured images as article thumbnails.
This is different from the add media feature at the top of the editor box.
If you don’t take advantage of this feature, usually the system will use one of the images that you uploaded via the add media feature to be displayed as a thumbnail.
How to use it is: Click Set Featured image >> Select an image, you can upload a new one or add it from an existing image.
This image on some template models, usually will also be shown at the top of the article.
Which is more important between this image or the one in the article? I think this WordPress Featured Image Feature is more important if you have to choose.