Concurrency in Racket

I'm having trouble understanding the concurrent aspect of Racket's threads. Can anyone provide an example and help me out a bit?

Specifically, I'm not understanding how they can be considered asynchronous. Why not call them coroutines if they just lock?

concurrency considered harmful

you don't need it outside of GUIs. if your code is too slow, parallelizing is not the answer!

nevermind, you need to wrap thread in a lambda.

>>2
jew

>>2
Ehh, if the computer is a multi core architecture or has a device that supports OpenCL, and if the program does not need to be sequential, then parallelizing can be the answer for better performance.

>>4
stop it