Event group
A set of bits, each meaning "this has happened", that a task can block on until one, some or all of them are set.
A semaphore is fine when a task waits for one thing. A network module that may only start once Wi-Fi is connected, the clock is synced and the config is loaded needs to wait on three conditions at once. An event group is an integer in which every bit is a flag: producers set their bits, and the waiting task blocks until the mask matches — any of them, or all together.
FreeRTOS added event groups in version 8 (2014), with 24 usable bits when the tick type is 32 bits wide. Other kernels call the same thing event flags. One detail tends to surprise people: setting bits from an interrupt in FreeRTOS doesn't happen immediately but is forwarded to the timer daemon task, because the operation can wake an unknown number of waiters and therefore has no bounded execution time.