Firmware is the code that is loaded onto a microcontroller that generally cannot be changed. It is one of three general terms categorizing the stuff of computing along with software and hardware. The firm refers to not being soft nor hard. It is in between. Often firmware is put onto chips before they are soldered into devices. When firmware can be altered it is usually a very risky process that can “brick” your hardware. Flashing the ROM of a device is one example of when firmware is updated.
⚠️ Firmware is one of the major attack vectors for hackers and has been responsible for the largest distributed denial of service attacks in history.