Wasm components
See the Component Model Explainer from the specification repository.
For a deep dive into the motivation and progress for the component model, see Luke Wagner's WasmDay keynote: The Path to Components.
Read Dan Gohman's What is a Wasm component and Joel Dice's The Wasm component model articles.
The core WebAssembly specification defines a portable binary format and compilation target for representing executable code. A core Wasm module can import functions, linear memories, or global variables from the host, or it can export them to the underlying execution environment.