The WordPress post editor contains an Excerpt field, which is described as ‘optional hand-crafted summaries of your content that can be used in your theme’.
These excerpts are traditionally used on search and archive pages, to provide visitors with a succinct description of the contents of a post. If you use the
the_excerpt() template tag, WordPress will display your custom excerpt, or if you don’t provide one, it will display the first 55 words of the post.
In my opinion it is always a good idea to provide a custom excerpt. For one thing, the first 55 words of a post won’t always describe the post fully, and may leave visitors guessing what the post is about. Also, if your post contains an image or video within the first 55 words, this will be omitted, which could mess up the flow of the text.
What we have done on Web Design From Scratch, is to edit our archive template, so that the post description is taken from the Yoast SEO Meta Description field. That kills two birds with one stone, providing a neat meta description, which also doubles as the post description on our archive pages.
This leaves the Excerpt field obsolete on our site, as it’s not used in our theme at all. However, third party services, such as Facebook and Google+, will still use the Excerpt where available, when people share a link to our site. For this reason, we also copy the contents of our Meta Description field into the Excerpt field, so that it’s available for any third party sites that want to use it.