Identifiers
A device on the PCI bus or USB is identified by two ID's which consist of 4 numbers and/or letters A to F. The vendor ID identifies the vendor of the device. The device ID identifies a specific device from that manufacturer/vendor.
A PCI device has often an ID pair for the main chip of the device, and also a subsystem ID pair which identifies the vendor, which may be different from the chip manufacturer.
Read more about this topic: Device Driver