Zones & imbalances
Splitting a move in half to buy cheap and sell expensive, and the 'optimal trade entry' zone.
Take a swing from its low to its high and split it at 50% (equilibrium). Above 50% is 'premium' (expensive), below is 'discount' (cheap). The idea is to buy in discount and sell in premium.
OTE (optimal trade entry) is a pullback into roughly the 62%–79% retracement of the swing: deep enough to be good value, while the swing is still intact. The 70.5% level, the middle of that band, is the one most often singled out.
All of this needs a real dealing range: a clear swing low and swing high that the current move started from. Measure a random stretch of chart and the 50% line means nothing.
For education only, not financial advice.