Permit means a permission to continue execution. Parking means suspending execution until permit is available.
Unlike Semaphore‘s permits, permits of LockSupport are associated with threads (i.e. permit is given to a particular thread) and doesn’t accumulate (i.e. there can be only one permit per thread, when thread consumes the permit, it disappears).
You can give permit to a thread by calling unpark(). A thread can suspend its execution until permit is available (or thread is interrupted, or timeout expired, etc) by calling park(). When permit is available, the parked thread consumes it and exits a park() method.