Geometric Brownian movement is a mathematical model used to describe how stock prices change. It's called geometric because it's like a shape that moves in different directions (up or down) over time. The Brownian part of the name comes from the mathematician Albert Brown, who studied the random movement of particles in liquid. In the stock market, the geometric Brownian movement model is used to predict how stock prices will change over time. It works by taking into account factors like the current stock price, how much the stock has gone up or down in the past, and how much it is likely to move in the future. Essentially, it tries to predict the behavior of stocks. It's like a math equation that helps us understand how stock prices will move.