WEBM is video the way browsers like it: open, royalty-free and built to stream. It was born in 2010, Google, out of its VP8 acquisition, and its real weak spot is life outside the browser: editors, TVs and Apple devices get picky.
Video is the heaviest thing most of us ever attach: screen recordings, camera clips, whole talks. Stands in for any video format Flippy can read: MP4, MOV, MKV, WEBM and the rest. That makes it the right destination when what you need is any moving picture: recordings, rips, exports, downloads.