Futures are usually assigned to a Task, which gets assigned to an Executor. When a task is awake, the executor will place the task into a queue, and will call poll() on the task until the process has been completed. Futures offer us a few convenient ways to execute tasks:

• Spawn a future task manually with futures::executor::block_on().
• Using futures::executor::LocalPool, which is useful for performing many small tasks on a single thread. In our future returns, we would not be required to implement Send since we are only involving the task on a single thread. However, you are required to use futures::executor::spawn_local() on the Executor if you omit the Send trait.
• Using futures::executor::ThreadPool, which allows us to offload tasks to other threads.