(0.9.0)
An unbuffered channel will block on calls to parallel\Channel::send() until there is a receiver, and block on calls to parallel\Channel::recv() until there is a sender. This means an unbuffered channel is not only a way to share data among tasks but also a simple method of synchronization.
An unbuffered channel is the fastest way to share data among tasks, requiring the least copying.
A buffered channel will not block on calls to parallel\Channel::send() until capacity is reached, calls to parallel\Channel::recv() will block until there is data in the buffer.
A powerful feature of parallel channels is that they allow the exchange of closures between tasks (and runtimes).
When a closure is sent over a channel the closure is buffered, it doesn't change the buffering of the channel transmitting the closure, but it does effect the static scope inside the closure: The same closure sent to different runtimes, or the same runtime, will not share their static scope.
This means that whenever a closure is executed that was transmitted by a channel, static state will be as it was when the closure was buffered.
The anonymous channel constructor allows the programmer to avoid assigning names to every channel: parallel will generate a unique name for anonymous channels.