This is the seder plate, and each food is symbolic for an aspect of Passover: A roasted shank bone represents the Pescah sacrifice, an egg represents spring and the circle of life, bitter herbs represent the bitterness of slavery, haroset (an applesauce-like mixture with wine, nuts, apples, etc.) represents the mortar used by the Jews in Egypt, karpas (or greens, often parsley) to represent spring.
Also placed on the table are three pieces of matzah — a cracker-like unleavened bread — that represent the bread the Israelites took with them when they fled Egypt, and salt water to represent the tears of the slaves. At your seat, you may see a specific wine glass (or kiddish cup). The Torah commands that (at least) four symbolic cups of wine be consumed during the Passover seder.