Talk from the first day of the conference by Mikola Lysenko.

In computer science, a fiber is a particularly lightweight thread of execution. Like threads, fibers share address space; where a distinction exists, it is that fibers use co-operative multitasking while threads use pre-emptive multitasking. Threads often depend on the kernel's thread scheduler to preempt a busy thread and resume another thread; fibers yield themselves to run another fiber while executing.

Mikola's own wording:
" Tango's Fibers represent a major step beyond
Phobos. From this single primitive, we can build a
host of patterns including coroutines, generators
and actor model processes -- all of which would be
impossible in Phobos. This type of flow-control is
invaluable when designing highly-concurrent
systems such as video games or web services.
This talk will focus on the Fiber API, some
applications and Tango's implementation. All
levels of experience welcome"

It appear that D programming language has first both really multiplatform and correct implementation of Fiber magic

Slides can be downloaded from: team0xf.com/conference/fibers.pdf