This is yet another “magical” directory that contains files that correspond to no storage. The /sys directory is used by HAL (hardware abstraction layer) to publish hardware information of a system. /sys differs from /dev in that /dev has a mostly flat organization, making it difficult to locate a particular resource by bus (such as USB, PCI, PCIe and etc.), class (such as block, character and etc.) or device (internally assigned name based on hardware).
Besides allowing applications access to devices, /sys also publishes information of such devices. For example, my phone is identified as follows:
Likewise, I can also find the product ID and vendor ID of my cell phone.