This is my understanding:

Look for "walls" on the left. The higher a green wall, the more people trying to buy at that price (prices along bottom). They have buy orders in so if it ever hits that value, it buys.

Walls on the right in the red are prices people have orders in to sell at.

You often see walls on either side at round figures, because humans be like that. "I'll sell when this hits $5/$10" kinda thing.

As a basic rule of thumb, the bigger the green wall, the more the price will rise when it "triggers" the buys and the bigger a red wall the more a price will fall. Like a huge red wall indicates lots are selling at that point, and supply is high.

I don't do this, but people watch these walls and see that they aught to sell before it hits (big red wall) because it will tank at that point.