Right now users do not understand where and how the uploaded Featured Image will be shown on the site

The area from where Featured Image is uploaded is very concise and does not have information on how the uploaded Featured Image will be used in the theme. This can cause confusion amongst the users who have not made their own theme. This issue can amplify if the uploaded image is used in different size through out the site and users will not test across the site and won't know how the image is appearing.

We can have short descriptions as suggested in the examples below to describe the behaviour of the uploaded Featured Image on the site.

Examples:

• The featured image will be shown on archives next to the optional excerpt of posts.
• 3 different sizes of featured image will be used: 50px - shown next to the post title in sidebar headlines. 150px - shown next to post excerpts on the homepage and archives. 500px - shown in the slider on the homepage.

This ticket was created based on a very old ticket on Trac (https://core.trac.wordpress.org/ticket/13522)