What Is A-Frame?

A-Frame is an open-source web framework for building virtual reality experiences, which you can use to build VR experiences for HTC Vive, Oculus Rift, Oculus Go and GearVR, Daydream, and Cardboard, with support for all respective controllers.

And if you don’t have a headset or controllers, there's no problem, because A-Frame still works on standard desktop and smartphones.