The Canvas Inbox is not intended to replace your email, but functions similar to email. Messages in your inbox are referred to as 'conversations'.

Why Use Inbox When I Already Have Email?

We are not asking you to abandon your school email for communication. But for the purposes of course facilitation and delivery, the messaging system in Canvas makes it easy to manage conversations by course, by section, by group and/or by student without having to know their email address or the distribution list.

Here are some other reasons to consider using the Inbox for course-related correspondence:

You can send messages to an entire course, just a section, or a student without knowing their email addresses.
When a student emails you, you'll know exactly which course he/she is enrolled in. No more replying "Who is this?" or "Which course are you emailing about?"
Conversations are threaded and kept organized by student name. So if Cindy sent 7 separate messages last week, you will only see her name in your inbox once -- all correspondence will remain together.
You can see the profile pictures of students (assuming they have added one) when reading student messages.
Your messages can be written in text or be recorded as a video or audio directly from the new message interface.
All messages sent via the Gradebook will be archived in your Inbox.
All comments made on assignments through the Speedgrader will be archived in your Inbox.

The following tutorials relate to conversations: