'Daddy, what's a Blu-ray disc?'
It's like a DVD, except it typically will not play in Daddy's laptop due to the extreme DRM crap. Yes little child, Daddy has a Blu-ray drive in the laptop.
Due to this DRM Gone Wild issue, Daddy has pretty much given up buying Blu-ray discs. Daddy just wants to watch the damn movie on his damn laptop. Cheap and Cheerful DVD's get this job done. Blu-rays not so much.