FIFO means????
FIFOs are often used to safely pass data from one clock domain to another asynchronous clock domain
FIFOs are used in designs to safely pass multi-bit data words from one clock domain to another.
In Async FIFO, Data words are placed into a FIFO buffer memory array by control signals in one clock domain, and the data words are removed from another port of the same FIFO buffer memory array by control signals from a second clock domain.
In Sync FIFO, FIFO where writes to, and reads from the FIFO buffer are conducted in the same clock domain.