At the end of the meal, we eat the Afikomen. This is the piece of the middle Matzah, which was broken in half and put away until now. Traditionally this has probably been "stolen" by somebody, most likely the youngest child and has to be “ransomed” because without it the Seder is unable to continue. The Master of the house will therefore, have to ‘bribe’ by a promise of a present to the culprit, to return the Afikomen. This adds to the excitement and participation of the children in the Seder. When it has been recovered it is distributed to all present who eat some of it together with a quantity of Matzah making up about half to three quarters of a sheet of Matzah.

haggadah Section:
Source: My Journey Through the Haggadah, Yekutiel Atkins