Google Chat is a school-managed service that allows employees and students in grades 6-12 to communicate via typed messaging. Designed for short, interactive exchanges, Chat is often faster and more convenient than email. Google Chat is an officially sanctioned chat app to be used between students and teachers. All Google Chat content is recorded and stored in an electronic Vault for later administrative access if needed.
Access the Google Chat service using any web browser at chat.google.com.
Log in using your d-e.org Google account.
Send direct messages to any other d-e.org account user, message a small group of of people, or participate in a discussion Room (such as one for a class or a club).
You can also access Chat in Gmail.
What can you do with Google Chat? - according to Google
Rooms and Threads
You can join or create a room as an easy way to use Chat for a class or to converse with a group of colleagues, or to work on a team project. Rooms have the advantage of supporting multiple conversations/topics in the same room as separate "threads". You can reply to existing threads or start a new thread at any time. The thread with the most recent activity shows as the bottom of the room messages.
You can choose to get chat notifications whether you use Chat in Gmail via chat.google.com open in a web page tab or by using one of the standalone apps. You can easily turn notifications off or customize them as you prefer. For example, you can choose to get only notified when someone sends you a direct message as opposed to when messages are posted in a Room where you are a member. You can also choose which rooms to actively follow. For more information on notifications:
Turn notifications on or off - How to enable/disable both email and push notifications/alerts for all messages are just for specific Rooms or topics (called Threads).
Temporarily stop notifications (Snooze notifications) - Disable all notifications on all devices with one step such as during a meeting or your disconnected quiet time.
While going to the web page chat.google.com works fine, some prefer having a separate program for using Chat. It also allows you to get notifications, if desired, without needing to keep a Chrome/Safari tab open to chat.google.com. If you just want to use the chat.google.com web page, you can skip this section.
Mobile apps for iPhone and Android and a standalone desktop/laptop program for Windows and Mac is available if you prefer that to using chat.google.com in Chrome or Safari. The mobile app is convenient for reading or responding from a phone.
For the desktop/laptop program, you should be prompted to install it if you are running Chrome or can start the install in Chrome using the directions in the Google support article Install the Chat standalone app here.
A few people have reported not seeing those options. If you have that issue you can install the desktop program from this download page. On a Mac this is slightly more complicated than installing from Chrome above as you need to move the Chat app into your Applications folder. Here is a video demonstration - Install Hangout Chat desktop on Mac.
Google Chat Help Center - by Google