Firmware can best be defined as:

Firmware is best defined as software that is permanently stored in a chip. This type of software is specifically designed to provide low-level control for a device's specific hardware. Unlike regular software that can be easily modified or deleted, firmware is often embedded directly within the hardware components, such as chips inside routers, printers, or other electronic devices. It serves a critical purpose, providing the necessary instructions for how the device communicates with other hardware and software.

This is why the other options do not accurately describe firmware. A type of volatile memory refers to temporary data storage that loses its information when power is turned off, which is not the nature of firmware. Temporary software for system speed improvements suggests a transient performance-boosting application, which again does not align with the permanence and stability associated with firmware. Applications installed on a hard drive refer to standard operating applications that can be modified or removed, contrasting sharply with the fixed nature of firmware.