This is incorrect. Orders and their distribution in the order book is called liquidity. Alone, they have very little meaning, and are often manipulated in the securities and commodities market(ie: you see a 5,000 bid, and place your own 5,000 ask - suddenly the bid is gone, and your ask gets rolled by huge buy orders). "Buy/sell curve" has no meaning, the closest term would be "yield curve", such as US interest rates. As the rate climbs and falls, there are inverse effects on financial instruments.