Yeah I was the same Kylie, has taken me 3yrs to get from basically being a computer nerd, to being a car nerd
You could just do what I did and ask here, I am sure people in this section can answer in an understandable way.
Plenum - To my knowledge this is the part after the throttle body on the intake, it feeds the air into the motor.
Blow Off Valve - This is basically a spring loaded valve, that when put under a certain pressure, it opens. Air comes in through your air box, or pod, then through your AFM (Air Flow Meter) and then into the compressor side of your turbo. From there it gets compressed and sent through piping to your intercooler. Then it goes through piping to the throttle body. A BOV usually sits on the piping at some point in it, before the throttle body so that when the throttle body closes, the compressed air is release out through the BOV and escapes instead of flowing back through the piping and out your turbo.
Imagine a straw (intercooler piping), at one end your finger is over the end (throttle body) at the other end is in your mouth (turbo). Now you can blow through it, but when you cover the end with your finger, the pressure builds, well if you had a BOV on the straw it would release the pressure, simple eh