Compared to creating walkthroughs in Word or Pages where you must use a separate screenshot app with additional steps involved, Clarify allows you to use the app to take the needed shots and automatically embed them. From there you can add instructions along with arrows and bullets to explain whatever it is you're trying to do. From there it can be exported into a clean and professional looking PDF for sharing.
Below is the aforementioned walkthrough for PowerSchool created using the app. I also used it to create one for Blogger last year that can be found here on a previous blog post.