An app that does virtually everything in terms of presentations. Use it to create lessons, activities, and assessments. It is an interactive whiteboard screen-type tool. You can import photos, pdfs, documents, video, audio, Powerpoint and Keynote slides directly from Dropbox or Evernote, email, or iPad camera roll. After annotating, narrating, or animating, you can export it as a movive or pdf files, sharing it easily with your students. Has a laser pointer to direct attention to specific content and an onscreen keyboard to add text directly to the presentation.
It is also easy for students to use. They can import a video or slides, draw on them, record an explanation, and then export it as a movie.
There is also a free book describing how to use it that is available at http://www.explaineverything.com/ibook--itunesu.html
How App is used in classroom/gym:
See how one physical educator has used Explain Everything to show how the iPad is the new physical education clipboard (also showcases many useful apps).