The post excerpt is commonly used by themes to display shortened “excerpts” of the content on certain website pages. One common example is when viewing a page of archives. Each archive may show an excerpt of the posts associated with that archive.
Another example may be when you click an authors link. The theme may show excerpts of each post that author has created.
Note; not all themes will use an excerpt area. It is up to the theme author when designing the theme to determine if a post excerpt editor is needed.
Post Excerpt Editor
If your theme does indeed use post excerpts; then there will be a box under the main content editor when creating/editing posts.
WP Edit Pro Post Excerpt
Notice in the screenshot above how the editor looks rather… bland. Where are all the cool buttons and ability to insert media?
The ability to add rich text to the excerpt area is not available by default. With WP Edit Pro, we can enable the standard content editor inside the excerpt area.
Go to the WP Edit Pro admin settings page -> General tab.
Check the option; and then revisit the post excerpt editor. It is now a duplicate of the main content editor.