These aren't side stories, they're the permission the main series gives itself to stop pretending plot matters and just commit to what it actually wants. Three minutes is the perfect length to deliver a joke, a fanservice beat, or a character moment before anyone has time to think too hard about it. If you came to NGNL for the games and the world-building, these will feel hollow; if you came for Sora and Shiro being ridiculous together in a world built for them, you'll recognize exactly what these are doing.
No Game No Life Specials is a set of six special episodes from 2014, packaged with the Blu-ray and DVD releases. The shorts blend comedy, ecchi and fantasy, and they serve as bonus material for viewers who pick up the home video volumes. They work best for fans who already know the franchise.