Charoset symbolizes the mortar that the Israelite slaves used to lay bricks. Like all traditional foods, variations abound. Traditionally charoset is served during the seder as a Hillel sandwich - which is charoset on matzo with horseradish. Sounds strange but it's actually quite delicious. Or maybe it just tastes good because by the time you eat it during a seder, you are so hungry you will eat anything!