Wyckoff & VSA
The ideas under the whole Wyckoff method: supply and demand, cause and effect, effort versus result.
Richard Wyckoff, writing in the early twentieth century, built his method on three laws. The law of supply and demand: price rises when demand is greater than supply and falls when supply is greater. The law of cause and effect: a trading range (the cause) builds up the energy for the trend that follows (the effect), and a bigger range supports a bigger move. The law of effort versus result: volume (effort) should match price movement (result); when heavy volume produces little movement, or a big move comes on little volume, a change may be coming.
He also suggested studying the market as if one large operator, the Composite Man, were behind it: buying quietly in ranges, marking price up, selling into the public's buying, and marking it down. It's a way of thinking, not a claim that one person runs the market, and it is the ancestor of today's 'smart money' idea.
For education only, not financial advice.