Coroutines are a very simple cooperative multitasking environment where the switch from one task to another is done explicitly by a function call. Coroutines are a lot faster than processes or threads switch, since there is no OS kernel involvement for the operation. Also coroutines require much less OS resources than processes of threads.
For a more complete definition of the term coroutine see The Art of Computer Programming by Donald E. Knuth.
This package contains the static library and header files used in development, plus developer's documentation.