After you begin using your school Apps mail account, you will notice in your inbox messages a list of contacts and a parenthesis number.

Apps mail groups all replies with their original message, to create a single conversation or thread. For example, lets say you send out an email about lesson plans to a group of teachers. In other email systems, the teachers' responses would appear individually as separate messages in your inbox, forcing you to wade through all your mail to see what people have said in their replies. In your Apps mail account, all messages related to the original email subject are displayed on one screen, in order, making it easier to understand the context of a message -- or to follow the conversation.