If you do a course announcement, then yes, the instructor may also be notified. Users can control what notifications they receive to their email, and these notifications can be turned off (but announcement notifications are on by default). Depending on the course settings, announcements may also appear in the Announcements page of the Course Navigation Menu, and/or on the course homepage (this is turned on/off from the course settings).
If you are using the Inbox, you can choose which users it goes to, which can include students and instructors, or just students. Inbox messages will always appear in the user's Canvas Inbox. Depending on their personal notification settings, inbox messages may go to their email as well.