When you Shepardize a document, you are requesting a comprehensive report of all the cases, statutes, secondary sources, and annotations that cite the document. This includes more recent cases that rely on the case you are Shepardizing. Basically, it tells you how the case was used subsequently, where it was being cited in other documents.
This is a quick way to validate your research to see if it is a good law or a bad law, if it has been affirmed or overruled, criticized or found void.
To Shepardize the document, click on the link next to the green diamond Shepardize this document. If you want to look at an immediate overview of the document, click on the Show signals slider.
The document will then have indications of the history and treatment of the document you are viewing. In this case, point 5 (see below) has positive treatment, meaning that it was cited as an affirmation or followed by other legislation. If you click on that signal, you can view what cited that section.
Once you have Shepardized your document, you are taken to a results page where depending on what you Shepardized, you can see the citing decisions from various courts. You can narrow your results on the left by the editorial analysis or the court or state in which the citation occurred.
When you click on a result, you will be taken to the section that cites the case you Shepardized. If you click on the Shepard's tab on the right, you will see the reason for the Shepard's Signal that was given to the document (in this case, a yellow triangle--indicating that there might be negative treatment such as being limited or criticized).