I'm fairly new to ubuntu and I've started to search around everywhere and check everything!
Recently I saw these files at /dev/input/eventX, js0, mice, mouseX. By printing the output using "cat" I realized they are somehow responsible for mouse and keyboard input but the output had an strange character encoding (even for the keyboard).

My questions are,

1. what are these files and how can I interpret the data of these files?
   


2. Are there any other places that I can access the input/output of my Ubuntu machine?
   


3. And are there any ebooks, manual or something similar that I can check the duty and structure of ubuntu system files? (i.e. to find the answer of such question)

Update

To make the data of the file more readable, I used hexdump:

sudo cat /dev/input/by-id/<nameofthemouse> | hexdump -C

[Source]