UARTS at a glance.

Universal Asynchronous Receiver/Transmitters (UARTs) are integrated circuits that convert bytes from the computer bus into serial bits for transmission. By providing surplus memory in a buffer, UARTs help applications by giving maximum throughput to high-performance peripherals without slowing down CPUs.
Early UARTs didn’t include buffering (RAM or memory). But with the advent of higher-speed devices, the need for UARTs that could handle more data became critical. Manufacturers then began adding 16-byte First-In First-Out (FIFO) buffers to UARTs for greater throughput.