Definitions for "Semaphores"
an apparatus for conveying information by means of visual signals, as with flags, etc.
An integer value used for signaling among processes. Only three operations may be performed on a semaphore, all of which are atomic: initialize, decrement, and increment.
Keywords:  wait, wants, locks, resource, access
When a work process locks a resource, it sets a semaphore. Another work process that also wants to access it must then wait.