A manual excerpt is the real summery for an article because it does not automatically pull content from anywhere. You must write out a manual excerpt yourself.
When creating/Editing a new post, there’s an “Excerpt” meta box available at the bottom for doing just that and here it is.
Note:
If you do not see it, it is most likely hidden by default. Scroll up to the top of the post edit screen and click the “Screen Options” drop-down. In there, make sure the “Excerpt” box is checked.
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