The title might not be clear enough because I don't know how to define my questions actually.
I understand Pthread is a thread library meeting POSIX standard (about POSIX, see wikipedia: http://en.wikipedia.org/wiki/Posix). It is available in Unix-like OS.
About thread, I read that there are three different models:
User level thread: the kernel does not know it. User himself creates/implements/destroy threads.
Kernel level thread: kernel directly supports multiple threads of control in a process.
Light weight process(LWP): scheduled by kernel but can be bounded with user threads.
Did you see my confusion? When I call pthread_create() to create a thread, did I create a user level thread? I guess so. So can I say, Pthread offers a user level solution for threads? It can not manipulate kernel/LWP?