Excerpts can be described as introduction or summary of your posts and represent only a small part of the full entry.
They are often used by our themes to display shortened parts of your posts, for example on the homepage, archives page or in the featured posts slideshow.
WordPress will automatically generate the excerpt from the first words of your blog post’s content.
However, you can also add a manually excerpt to your post in the Excerpt metabox. It is usually located below the post editor. If you do not see the Excerpt metabox, check your screen options.
Please be aware that WordPress excerpts are text only. WordPress does remove all text formatting, images and other media from the automatically generated excerpts.