updates README.md

Author: Brennan Stehling

README.md

@@ -6,5 +6,12 @@ When the `next()` function is called it is expected to return a value asynchronu
 If the values are not created in response to calling this function these values will have to be provided
 somehow. This channel supports sending values which the `next()` can return.
 
+In the unit tests, a channel is created and given to the sequence. When the iterator is created it is
+given the same channel. Calling `send` on the channel will make new values available. When the `next`
+function is called it creates a `continuation` which will be matched to a value so it can be returned.
+Calling `terminate` will use a `continuation` to send `nil` which tells the for loop it is done.
+
+All of the work done by the channel is done as an actor type so that it is thread-safe.
+
 [AsyncSequence]: https://developer.apple.com/documentation/swift/asyncsequence
 [AsyncIterator]: https://developer.apple.com/documentation/swift/asyncsequence/asynciterator