The seder plate holds the symbolic foods of the Passover seder in fixed positions, and each item is placed there to prompt a question and carry a meaning in the retelling of the Exodus.
The items and their sense
The plate arranges the shank bone for the paschal offering, a roasted egg, the bitter herb for the bitterness of slavery, the sweet paste that recalls the mortar the Israelites worked, another bitter vegetable, and the green vegetable dipped in salt water, each in its appointed place. During the seder these are pointed to, lifted, and eaten at set moments as the Haggadah is recited, so the plate is not a centrepiece but a working script, the foods cueing the parts of the story in order.
Telling through the senses
The genius of the arrangement is that it turns the retelling of the Exodus into something tasted rather than only spoken, the bitterness of the herb and the sweetness of the paste making the account of slavery and hope physical, and the unusual dippings and orderings are designed precisely to make a child ask why this night is different. The positions of the items are fixed by custom, with differences between communities, and the plate itself, often a fine dish made for the purpose, is among the objects a family keeps for the festival. It is inseparable from the Haggadah, the two together carrying the seder.