If you want to put your video files online using HTML5 then it's recommended to have three different formats for a full browser support. Those formats are mp4, ogv and webm.
If you want you can turn any Microsoft PowerPoint presentation into a video so you can play the presentation on a computer that doesn't have Microsoft Office installed.
TinEye is a great reverse image search online service, that can tell you where an image came from, find different sizes of the image and you can find out if someone is using your image without your permission.