Question: Why may one not drink between the third and fourth cups?

Answer: In order that he not get drunk and be unable to recite the Hallel.

Objection: But he already drank wine during the meal! What is the difference whether he drank during or after the meal?

Wine after the meal causes intoxication but wine during the meal does not.

Question: What is Afikoman?

Answer #1 (R. Simon quoting R. Inaini bar R. Sisai): Singing songs (which are customarily sung after eating; instead of these, Hallel will be recited afterwards).

Answer #2 (R. Yochanan): Types of sweets.

Answer #3 (Shmuel): Like the mushrooms and young bird meat that Chananya bar Shilas would serve after a meal.