LinuxQuestions.org - Interpreting lsusb output

I have trawled through numerous sites however none of them give a detailed explanation of the output produced by lsusb. Here is an example of what I see

Code:

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 002 Device 003: ID 046d:c019 Logitech, Inc. Optical Tilt Wheel Mouse

Bus 002 Device 004: ID 04f2:b044 Chicony Electronics Co., Ltd Acer CrystalEye Webcam

1. What doe the Bus and Device refer to? I can see that I have 2 USB ports on each side which gives me a total of 4. How are these related?

2. What does Linux Foundation 2.0 root hub refer to?

3. What does Intel Corp. Integrated Rate Matching Hub refer to?

I then have the ls output of the path /sys/bus/usb/devices

Code:

1-0:1.0  1-1:1.0  2-1      2-1.2      2-1.5      2-1.5:1.1  usb2

1-1      2-0:1.0  2-1:1.0  2-1.2:1.0  2-1.5:1.0  usb1

How do I match the ls output to what I see in lsusb?