Clock speed is the rate at which a chip’s clock can generate pulses, often by using a crystal oscillator. Generally processors (especially CPUs) are described in terms of their clock rate.
Many computers from decades ago began with a frequency in the kilohertz (kHz) or megahertz (MHz). From there, we had huge increases in clock speed which in part helped us keep up with Moore’s law. Since 2010 or so, CPU clock speeds have largely levelled out at a few gigahertz (GHz) and haven’t increased since. Prof Najm mentioned that one of the reasons we can’t keep increasing is because of power dissipation within the chip. Nowadays chips draw a LOT of power so higher frequency means more power is dissipated.
The main implication of this is that for increasing chip performance, we increasingly use multi-core processors, so it’s important to know parallel computing.