The Constant Product Formula is expressed as x * y = k, where x and y are the quantities of two assets in a liquidity pool, and k is a constant. This means that the product of the quantities of the two assets remains the same, regardless of the amounts traded. This formula is fundamental in platforms like Uniswap and PancakeSwap, allowing trades to occur without the need for order books or centralized control. When a trade occurs, the quantities of x and y change, but their product (k) remains unchanged, ensuring liquidity availability while determining the price based on the ratio of the two assets.