WebXR is a technology that allows developers to create immersive experiences on the web. With WebXR, developers can create augmented reality (AR) and virtual reality (VR) experiences that can be accessed by users on a variety of devices, including smartphones, tablets, and head-mounted displays.
The WebXR Device API provides access to input (pose information from headset and controllers) and output (hardware display) capabilities commonly associated with Virtual Reality (VR) and Augmented Reality (AR) devices. It allows you develop and host VR and AR experiences on the web.
You can read more about the goals and effort by reading the WebXR Explainer.