Consise description of Async model missing from "Why Async?" page

[softmoth]

In the Why Async? » Async vs. other concurrency models section, there is no description of Async itself. It's frustrating reading through the whole page and finding lots of descriptions to the contrasting models, but no concise description of what constitutes the Async model in Rust.

Please provide a definition of Async, similar in detail to those provided for OS threads, event-driven, coroutines, and the actor model. Then the phrase "In summary, asynchronous programming allows..." could accurately be called a summary of something.

Thank you!