Matches are created when Jobs are found that match any of your Searches.  The specialty, type of position, location, date the match was created, and a % showing how closely the Job matched.

Click the Specialty to view the details of the Job:

Once you've reviewed the Job and you're interested in more information, you can contact the Hiring Authority.  Their contact information is listed in the Job details.  Also note that this Match shows for the Hiring Authority as well, so they may contact you.