Before entering the market, lay a solid foundation first! This article deeply dissects the five core mechanisms of foreign exchange and Contracts for Difference (CFD): analyzes how leverage amplifies capital efficiency and how to calculate the liquidation red line, explores the all-weather hedging logic of long and short two-way trading, and clarifies the lifeline relationship between margin occupation and dynamic risk control. At the same time, we look into the hidden costs of holding positions such as spreads and overnight interest, allowing you to gain insight into the nature of the price game of "not holding physical objects, only trading spreads" and avoiding cognitive blind spots.