Uploading App to Google Play - Demo App Video or a Feature Video


I am not sure if this is a right forum to ask, but just had this question in mind and it would be great if I can have authentic answers which I can try out myself.
How do you create a feature video or a demo video of an app? I was thinking about uploading an app to Google Play wherein I learnt that in addition to having screen-shots of the app adding a demo video or a feature video will help no end.

Any suggestions from app developers here in the forum who can help me out please?