By Rabbi Pinchas Kantrowitz

Rabban Gamliel used to say: "Whoever does not explain the following three things at the Pesach festival, has not fulfilled his duty, namely: the Pesach offering, matzah, and maror."

Matzah represents freedom. Just as our ancestors did not have time for the bread to rise when they were leaving Egypt, we relive the Exodus by eating the bread of redemption.  

Maror represents servitude. The preferred type of maror is one which begins sweet and becomes bitter, just as the lives of the Jews in Egypt commenced in comfort and sweetness, but terminated in bitterness and servitude.

What is the significance of the Pesach offering, and why must it be eaten together with the matzah and maror? The Maharal of Prague teaches that the Pesach offering represents oneness, unity. The Paschal lamb or sheep is a "groupee," an animal which associates with its flock. It may only be eaten by one who assigns himself to a group, and only in a single house or location.  Even the structure of the meat must be retained, as the meat must be eaten roasted (roasting shrinks and unifies the meat, as opposed to stewing which breaks the meat apart), and a bone must not be broken in the meat, to retain bone structure. 

The exodus from Egypt occurred in a generation when Jews were identified with the nation. Our Sages teach us that the final redemption will parallel the exodus from Egypt, and necessitates the unification of the Jewish nation.

Why must the Pesach offering be eaten together with matzah and maror? Because it represents the offering to the One G-d who is capable of decreeing servitude (maror) and redemption (matzah) for one ultimately beneficial purpose, the creation of a unified nation, loyal to the One G-d.