Firmware is the code that controls an electronic circuit at the lowest level. Firmware is usually stored in ROMs or flash memories and contains the necessary instructions for the software to interact with the hardware of a device. The use of this term has become widespread and is adopted to refer to any content stored in a read-only memory (ROM).
Device manufacturers offer firmware updates to improve functionality and fix device bugs. An example would be supporting new security mechanisms on a device that has WiFi.
From a cybersecurity point of view, access to firmware is essential to identify security problems in devices. This firmware can be obtained in some cases directly from the manufacturer or by accessing the memory chip through hardware hacking techniques.