A buffer is used for communication between objects which run in different threads. A buffer wraps some shared memory or a unique pointer thereto. The buffer may be accessed by the two communication partners via reference to the buffer which is initialized via constructor argument.
A buffer is a single block of memory for a message (or unique pointer) and messages are not queued. Check out the channel if you need communication via a message queue.
Object-oriented semaphores are not part of the C++ standard at this point. However, it is possible to implement a semaphore class using a mutex and a condition variable both of which where added to the standard in C++11.
For the implementation shown on this website the function names where derived from the POSIX semaphores. The post function increases the count of the semaphore and notifies a thread that might be waiting on the semaphore if its count is at zero.
How to stop a thread. It is a nice idea to create a functor (overload operator()) and pass a functor object to a thread. The operator()() (line 9) should generally contain a while loop (event loop)(line 10). To be able to stop the while loop from the outside, one can use a member variable of the functor, e.g. bool IsStopped or bool IsRunning (line 15). The loop would then look like this