So, why do we  have these random things on the seder plate?

Each thing actually represents something.

That disgusting bitter herb over there symbolizes the bitterness of the Jewish people.

The shankbone symbolizes the strong arm of God that took us out of Egypt.

The egg is the cirle of life.

Probably the best tasting thing on the seder table which is the charoset represents the cement that the Israelites would havre to mush up by steppin in it.

haggadah Section: Cover
Source: Original