A USB Serial Converter driver is software that allows your computer to communicate with devices through a USB-to-serial adapter. These adapters are commonly used to connect older serial devices (which typically use DB9 or DB25 connectors) to modern computers that may lack serial ports. Examples of such devices include industrial equipment, legacy systems, networking hardware, and embedded systems.

When you plug a USB-to-serial converter into a Windows machine, the driver is required to create a virtual COM port (like COM1, COM2, etc.) that enables communication between the USB adapter and the software you're using (like terminal programs or custom applications).