Kind of hard to describe, tweaking is a feeling you get that is like a rush of energy that forces you to stay up or be overly active. There is even an energy shot like 5 hour energy they sale at continence store called tweaker. Because that is the term for that burst of energy. Any drug that gives you a shot of energy or prevents you from sleeping is tweaking. I have ate shrooms a couple times and it has it's moments but the tweaking feeling and pupils getting huge are the big turn off for me. I wouldn't do it again.
I have done Shrooms a couple of times. I wouldn't go back either. Too unpredictable for me to trip again.