Thanks, but I hope you can see why I find this language a little opaque. "Type thread represents thread" is circular.
I take that the Lua engine implements it's own lthread infrastructure, which is non-pre-emptive. Yeah? So a Lua thread is basically a set of state data - an environment in which code executes. Afaik exactly parallel to any generic threading lib like pthreads (where a "thread" is actually a data structure). No? (I confess I find the language of threads confusing in general.)