Teachers can post all their class content in one place, including a calendar for due dates, links to class resources like videos, posted homework assignments (and a drop-box for turning it in), etc.
Students can see all their assignments, due dates, and class materials in one spot. They can turn in assignments and see teacher feedback.
Parents can create accounts so they can get a glimpse into the classroom, see what assignments are in the works, keep an eye on due dates, etc.
Benefits of Canvas
Ease of use, ease of navigation, user-friendly interface, improved communication, calendar, notifiactions, rubrics, multi-media integration (create and add audio/video directly and even add these types of comments when grading with Speedgrader), mobile app, and more.