Understanding NSPR threads

Hello,

I have read very carefully "Chapter 3, Threads" in the online
documentation, but I must admit that I have a hard time understanding
the API. First of all I do not exactly understand the distinction between

PR_LOCAL_THREAD
	A local thread, scheduled locally by NSPR within the process.

PR_GLOBAL_THREAD
	A global thread, scheduled by the host OS.

PR_GLOBAL_BOUND_THREAD
	A global bound (kernel) thread, scheduled by the host OS

Can some kind soul explain to me what this means in terms of Unix/Linux
pthreads? What is a "global bound kernel thread"?

IMHO, the whole chapter seriously needs revision, and I am willing to
read through it again and give my comments (in case that someone is
interested).

Greetings,
Joachim