This driver will let you use USB to serial programmable devices with the ch340g/ch340c/ch314 chipsets. These programmable chips are used for small projects and some devices that have been converted for USB. There is a tutorial here on installation and other functions of the chip. If you are installing on a really old version of Windows such as Windows 98 make sure you install all the latest drivers for USB support, sometimes the unofficial Windows 98 Service packs are the best way. Devices using ESP8266 Chipset are often interfaced with the CH340 chip.