The WebAssembly Working Group has published three First Public Working Drafts:

WebAssembly Core Specification describes version 1.0 of the core WebAssembly standard, a safe, portable, low-level code format designed for efficient execution and compact representation.

WebAssembly JavaScript Interface provides an explicit JavaScript API for interacting with WebAssembly.

WebAssembly Web API describes the integration of WebAssembly with the broader web platform.

WebAssembly is a virtual instruction set architecture with many use cases and can be embedded in many different environments, that enables high performance applications on the Web. The design goals of WebAssembly are fast, safe, and portable semantics; efficient and portable representation. WebAssembly code is also intended to be easy to inspect and debug, especially in environments like web browsers.