Find the afikoman and distribute it to all who are seated at the table.

When the Temple still stood in Jerusalem, it was customary to make an offering of a paschal lamb at this season. Now we eat the afikoman in memory of the offering.

Tzafun means “hidden,” and the afikoman is usually hidden for children to find. Why end the meal thus? Because we want the dinner to end with the taste of slavery/freedom in our mouths—thus the taste of matzah, rather than some unrelated sweet.

But this explains eating matzah late, not the charade of hiding it. The hiding works on two levels: it intrigues the kids—and it allows us to affirm our sense of the Hidden and Mysterious. On this theory, we hide the larger half of the broken matzah because we are affirming that there is more that is Hidden and Mysterious in the world than any information we can gather. 

haggadah Section: Tzafun
Source: Velveteen Rabbi's Haggadah for Pesach