At the top of certain text areas in the edit form, there is a link to ‘edit summary’.
By default, the first 250 characters of the post (page, article, etc.) will display on lists described as "(summaries/teasers)", on the home page, and as blocks in the sidebar. There are a few ways to customize this summary.
The easiest way is to change where the content breaks for the summary is by using the teaser break button. Click within the text area where you’d like the summary text to break and insert the teaser break by clicking the icon. This will insert the following:
If you don’t want a summary for a certain article or page, just insert the break at the very beginning of your content.
You may also click ‘edit summary’. This will expand a separate text area where you can include custom text and/or images for the summary. You can enable the WYSIWYG on the summary by clicking the 'enable rich text' link below the expanded summary field.
Using Summary and Break to make your lists look great
The image below is an example of a List. In this case, the List page is titled "How-to" and the two items appearing in red, "Managing Files" and "Create a photo album," are Basic pages that have been tagged with the term "how-to" to cause them to appear in this list page.
Under "Managing Files," you will note the teaser is rather long and cuts off in the middle of a sentence. In that article, the teaser was not set in a specific location, so it is being automatically broken after a certain number of characters.
By contrast, the "Create a photo album" page uses a brief teaser that has been made to stop at the end of a sentence.