I recently found out about the lsusb command while troubleshooting a headset issue..My laptop runs debian and doesn't have anything plugged into USB currently, but when I run the lsusb command, I still get quite a bit of output:root@t500:~# lsusbBus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hubBus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hubBus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hubBus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hubBus 004 Device 003: ID 0a5c:2145 Broadcom Corp. Bluetooth with Enhanced Data Rate IIBus 004 Device 002: ID 08ff:2810 AuthenTec, Inc. AES2810Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hubBus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hubBus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hubBus 001 Device 002: ID 0781:b6d0 SanDisk Corp. Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hubCould someone break down what this means in more detail?The SanDisk card is connected via PCMCIA, not USB.  Are both PC cards and USB devices listed in lsusb?I don't have any external bluetooth connected, why would this display?Why are some root hubs 1.1, and some 2.0?  Does that mean some of my USB ports are 2.0 and others aren't?What is a root hub exactly, just an empty USB port?
How to interpret the output of 'lsusb' -- What are all these Linux Foundation root hubs?
debian;usb
A USB hub is a device that has one cord that plugs into one USB port, but provides multiple USB ports for you to plug devices into. It's essentially a USB multiplexer.A root hub, AFAIK, is a USB hub that's internal. For example, there might ony be one USB slot in your motherboard, but there are multiple external ports because there's an internal root hub plugged into the motherboard. (This is simplified, of course. I'm not an expert in hardware.)The Bluetooth device is the chip inside your computer that actually broadcasts Bluetooth radio traffic. Probably, it's wired through a USB port inside the computer's case.With regards to the display of Linux Foundation, my guess is that that's where the drivers come from. But I'm not sure.