It's a ceremony involving contrasts, opposites. We starve (during the sometimes seeming unending recitations and discussions) and we also feast, not only on the festive meal but a number of ritual foods.
Contrasts start with the "four questions" traditionally recited/sung by the youngest capable attendee at the seder:
1. On all other nights we eat bread or matza, while on this night we eat only matza.2. On all other nights we eat all kinds of vegetables and herbs, but on this night we have to eat bitter herbs.3. On all other nights we don't dip our vegetables in salt water, but on this night we dip them twice.4. On all other nights we eat while sitting upright, but on this night we eat reclining. (about.com)I understand that this is to get the child involved, but the answers aren't very clear and relevant to a child's understanding. I'm a former remedial teacher, and I can't see how "because we were slaves to Pharaoh in Egypt..." would make much sense as an answer to why we dip our vegetables in salt water.
Of course the children may and should insist on better answers if dissatisfied with the Seder's text. The next big contrast are the supposed questions of four different types of children. The compilers of the Passover Hagadah recognize that we're all different and so are our children. Also it's important to welcome all Jews to the seder no matter what their level of observance. That is important and very different form many other Jewish rituals which quickly become rejected and forgotten by those who aren't Torah observant. The Passover Seder is one ritual that many people make an effort to observe, even partially, no matter how far they are from Torah living.
Four Blessings, Four Children
Blessed is the omnipresent one, blessed be He!Blessed is He who gave the Torah to His people Israel,blessed be He!The Torah speaks of four children: one wise, one wicked, one simple, and one who does not know how to ask. (Chabad)
What does the wise one say?“What are the testimonies, the statutes, and the laws that G‑d, our G‑d, has commanded to you?” (deut. 6:20)What does the wicked one say?“What is this service of yours?!”12 The Simple One—what does he say?“What is this celebration about?”As for The One Who Knows Not How To Ask—you must open up [the conversation] for him.
Judaism is an open religion in many ways. We communicate directly with G-d, and we were given Free Will. G-d did not create us to be robots or angels, who can be described as G-d's robots. Human beings were gifted with the abilities to make mistakes, yes, even bad ones, and to repent, do teshuva. Many families contain all versions of these four children.
The ritual meal at the seder opens with a food combination that symbolizes our families, the Jewish People, when we combine the sweet charoset* with the sharp, burning bitter herbs**. First they are eaten together, just the two contrasting foods. And then we (most Jews, at least those who do not have the minhag, custom forbidding matzah to to touch any other food) make a sandwich of it between two pieces of matzah.
When we eat this combination we should remember that G-d loves us all, as a Father. That isn't a green-light to disobey His Laws; it should remind us that G-d wants us to improve ourselves and live according to His Laws.
*our charoset recipe
chop up apples, walnuts, almonds
mix together and add cinnamon and sweet red wine
romaine lettuce and/or horseradish root, which we grate and add a bit of vinegar to keep it potent