[chuck-users] Where are details like 'chout' and '<=' documented?

Searching online I found one example for 'chout' -- which I was able to use, except that I've got no idea what it's doing aside from the fact that I can plug a string I want to send out into that example. And I can't find (so far) documentation that tells me why this example is written the way it is, or even that such syntax is even in the language. Where? -- (Help?!!!)