The SharePoint 2010 Search Center results page contains a new section called the refinement panel. This panel is located on the left portion of the screen and provides a summary of search results which, when used, act as filters on the returned data.
Out of the box, there are three main categories:
Site
Author
Date
New custom refinement categories can be configured, these are based on managed properties. Managed properties are the metadata stored with items in SharePoint. There are many more properties than the three that are shown out of the box.
This recipe consists of two parts:
Adding a managed property, which takes place in the Central Administration.
Modifying the refinement menu to include a new category based on the managed property, which will be done at the site level.