Some seder plates have spaces for five items and others for six. The additional item is hazeret, horseradish, which serves as a second bitter herb. With seder plates that have six holders, many people will use pieces of horseradish root for the maror (bitter herb) and ground horseradish for the hazeret. This article, written from a traditional perspective, also makes mention of a particular type of seder plate that sits atop a holder for the three matzot used at the seder. Most seder plates do not come with the matzah plate attached, and the matzah therefore sits on its own, separate plate. Excerpted from Celebrate! The Complete Jewish Holiday Handbook (Jason Aronson Inc).