dear one,
pretend you are a lamp, and you are plugged and everything is working great,
then suddenly the light bulb starts blinking on and off, you cant read - you stop and start reading, but you can finish what you are doing until the circuitry is connecting correctly...
so on is - the light is on -all is working- circuitry receiving signals -
off - when you can completely walk because the almighty cord to the wall -
(the neurotransmitter) is not receiving or transmitting a signal correctly,
so the light bulb is either blinking or it is out = off.

they say freeze also - which is like - you can't move, - I have done this, but now I know a trick that helps, -
I was told by a brain surgeon when a patient freezes his/ her movement:
it is because the eyes are stuck in a gaze...
but do not worry Lloyd as it may not happen to you.
We mayactuallyfind the cure....
I have had PD a long decade
and it is my great hope, they will cure us soon...

hope you understand the analogy?
best I can do unless -you click the young onset moviein the signature of my post and watch -
a very good selection of young onset PD patients/ my great friends have allowed us a peek inside their world of coping with PD.
and their are neurologist that also explain it ...