Yachatz is the breaking of the matzah. It is the fourth step in the seder. Three pieces of matzah are taken out of a white bag and the middle one is broken. The bigger one is hidden somewhere in the room. You will be looking for it later in the seder. It is called the afikomen. The smaller piece is kept in the matzah bag. The word yachatz means dividing. There are three matzahs to symbolize Abraham, Isaac and Jacob. The middle piece is broken to symbolize the binding of Isaac. The binding of Isaac is when God told Abraham to sacrifice Isaac as a test to see if Abraham would listen to him. God told Abraham to stop just as Abraham was about to sacrifice him.

haggadah Section: Cover
Source: google