What major events take place in this Chapter 16 of To Kill a Mockingbird?

The study guide for Lee's novel gives a full answer to your question. It identifies three new characters that are introduced, including Dolphus Raymond, who's discussed in the previous post. It also gives a summary and a discussion; both are worth checking out.

I'll add that what I find most interesting about this chapter are the pre-trial festivities (it's a "gala occasion," the novel tells us); Jem, Dill, and Scout's discussion of the "one-drop rule"; and the segregation of the blacks both outside and inside the courthouse. Jem, Dill, and Scout sit in the balcony with the black spectators, but they aren't there as equals. Black people seated in the front row of the balcony stand, giving up their seats to the white kids in a gesture that reminds me of the Jim Crow rules that lead up to the Montgomery Bus Boycott in the mid-1950s.