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.
GIF is the internet's court jester: 1987 technology that still runs every group chat. An animated image format: every frame is stored with a 256-color palette, there's no audio track and no inter-frame compression. That makes it the right destination when what you need is short, silent, autoplaying loops that work absolutely everywhere.