A kHz, or kilohertz, is a measurement of frequency equal to 1,000 Hertz. Kilohertz is unit of measurement for alternating current, audio signals, and a measurement of wireless signals. With circuits, an oscillator circuit supplies a small amount of electricity to a crystal each second that is measured in kHz, MHz, or GHz. "Hz" is an abbreviation of Hertz, and "k" represents Kilo (thousand), "M" represents Mega (million), and "G" represents Giga (thousand million).
The first CPUs (central processing units) operated at speeds measured in kHz. For example, the first processor, the Intel 4004 operated at 740 kHz. Later processors operated in MHz, for example, the Intel Pentium processor was available in speeds of 60 MHz to 300 MHz. Today's processors operate in the GHz. When measuring the speed of a processor, the higher the speed (bigger the number), the faster it is capable of running.
Should I capitalize the "k" in "kHz"?
No, the "k" in "kHz" is always lowercase.