This video from the Canvas guides explains the basics of setting up and using discussions.
516a - Discussions Overview from Canvas LMS on Vimeo.
Discussions can be a great place to do student introductions at the beginning of the quarter. A teacher can create a discussion with their own introduction as the description and then encourage students to create their own. This can be taken a step further as you can encourage students to attach images or a short video of themselves answering get to know you questions to their posts.
Discussions can be graded and used as a means to discuss or debate current issues related to the course. Encourage students to thoroughly research the subject and then open the discussion topic up, allowing them to share their findings with one another. To incentivize student participation, it may be helpful to ask students to post or comment on other's posts a certain number of times. It may be helpful to assign groups of students to one side of the debate or another.
You can create a discussion with no due date and an availability window that spans your entire course as a place for students to engage with the professor and one another. This can be a place for students to ask questions that they feel would benefit their classmates, to post comments or helpful links and resources for one another. This creates a unintimidating and collaborative environment for students, encouraging them to participate in this and other discussions.