The primary goal of WebAssembly is to "enable high performance applications on the Web." Specifically, compiled WebAssembly applications are intended to execute at the same speed as native applications "by taking advantage of common hardware capabilities available on a wide range of platforms."
This will make it possible for a wide range of software, including games, image and video editing, low-latency augmented and virtual reality, and remote desktop, to be implemented as browser-based applications. Currently the four major browsers, Firefox, Chrome, Safari and Edge all support WebAssembly.
The WebAssembly Working Group includes Mozilla, Microsoft, Apple and Google among others. More information about WebAssembly can be found on the WebAssembly website.