It’s a lot like Powerpoint in that you create a file that’s essentially a presentation. However, each slide can be a video tutorial, or it can be an image with annotated comments when you roll over parts of the image. It can just be text.
Where it gets particularly useful for the classroom, is with its use of built-in assessment tools. So, you can create a stand-alone lesson and then quiz students at the end of it. The results of the quiz can be stored and even interface with an integrated learning system. As mentioned, I thought this could be useful for differentiated instruction, or also for formative assessments of complex topics.