Curious about lsusb output

Question

I ran lsusb on my Linux (Ubuntu) machine and here is my result:

Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 003: ID 413c:2005 Dell Computer Corp. RT7D50 Keyboard
Bus 001 Device 004: ID 413c:3016 Dell Computer Corp. Optical 5-Button Wheel Mouse
Bus 001 Device 005: ID 03f0:a007 Hewlett-Packard 

The last 3 entries are my USB keyboard, mouse, and headphones which makes sense since I have them physically plugged into the computer. I am confused on what the Linux Foundation 2.0 root hub and the Intel Corp. Integrated Rate Matching Hub is.

I also am wondering why some of the entries are listed twice and what the difference is between 'Bus' and 'Device'. Some of the entries are on bus 001 while others are on bus 002.

Answer 1

That is probably usb units found on your motherboard.

And the bus tells you about where the unit is connected, more or less what usb controller is handling the device.