What Are Tasks?
You can think about tasks in a variety of ways. One is to start from the notion of a thread and state that tasks are like lightweight threads, running on top of a pool of low-level operating system threads. This is quite an implementation-oriented definition that starts from machine-level mechanics and builds an abstraction out of it.
A better way to think about tasks is to see them as representations of future values that get computed by means of a function. As such, tasks are sources of asynchrony in your code: While the task is running, you can do other useful work, until the point you want to await the task’s result. Furthermore, tasks can be composed in a variety of ways.
In the definition in the preceding paragraph, the ...