Linux supports a wide variety of USB (universal serial bus) devices. A USB system on a PC consists of a host controller inside your computer, hubs that act as splitters to give you more ports, and the actual USB devices. The Linux kernel supports USB devices through three types of drivers:
Host interface drivers
USB device drivers
Other drivers not necessarily related to USB, but required by a USB device driver (for example, the USB mass storage driver requires the SCSI disk support driver)
When the host interface driver recognizes a controller, the kernel logs messages such as these:
ohci_hcd: 2003 Oct 13 USB 1.1 'Open' Host Controller (OHCI) Driver (PCI) ohci_hcd 0000:00:02.0: irq 9, pci mem d4806000 ohci_hcd 0000:00:02.0: new ...