At the start of this chapter, the whole community is going to the auditorium to watch a bunch of ceremonies. There are going to be a lot of different ceremonies that will take place on this particular evening, but the most important of these is going to be the Ceremony of Twelve.
The ceremonies happened only once each year. On those days, the whole community would go to the Auditorium to participate. There were ceremonies ranging from the Naming (where newchildren are given names) to the Ceremony of Twelve. In this ceremony, all of the kids who are reaching age 12 are assigned to the jobs that they will hold for all of their working lives.
When the chapter begins, Jonas and his family are putting on their nicer clothes. Jonas' mother is worried about Lily's ribbons becoming untied, and it is clear that she wants everything to look good. Eventually the reader finds out why. Jonas's family is getting ready to head to the Auditorium, where there will be a series of ceremonies. The text says that this event happens only once per year, and that all of the working adults get two days off of work for it.
The ceremonies are focused on the children and their advancement to the next age and the responsibilities and privileges that it brings. The first ceremony is the ceremony of the naming. This is the ceremony where the youngest children are placed into their chosen families. The ceremony that is the biggest deal of all is the ceremony of the twelve. This is the ceremony that declares what the job of each new twelve-year-old will be.