do i need to upload a video preview when i sell a template?

the “step by step” of how to sell a template talks
about uploading a preview GIF, and thumbnail.
however when look at templates at the sites there is alaways a short video as a preview of the template?
do i need to upload a video?
is the GIF preview needed to be a sequence so it can be used a video?
if anyone can give me answeres about it, it will be great, thanks

Yeah, a video not a GIF. I’m curious where it says GIF though, I’ve never seen that?

right here in “image preview”