Executor
The Executor is the working horse of the asynchronous processing. He pretty much represents the runtime that is able to continuesely request the result of every Future until they return the Ready state. Registering a Future at the Executor to allow the same to run it to completion is called spawning. As part of this the Future is wrapped into a structure that allows proper handling of processing and re-spawning of pending futures. In the Rust libraries this wrapper is typically called a Task.