The unit of computer speed is generally measured in Hertz (Hz), which represents cycles per second.

However, since modern computers are very fast, speed is often expressed in:

• Megahertz (MHz): One million Hertz.
• Gigahertz (GHz): One billion Hertz.

The clock speed (measured in Hz) indicates how many instructions the processor can execute per second. However, it's important to note that clock speed isn't the only factor determining a computer's overall performance. Other factors include the processor's architecture, the amount of RAM, the speed of the storage devices, and the efficiency of the operating system.

For example, this Intel Article discusses CPU Clock Speed and performance.