Market depth (or "depth of market") shows the pending buy and sell orders stacked at different price levels around the current market price, revealing how much volume would be needed to move the price a given distance. Traders use it to gauge where large orders are clustered and how liquid the instrument is at that moment.
Deeper markets absorb large orders with less price impact, while thin depth means even a moderate order can cause a noticeable price jump.
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Guide
How Execution Models Work: ECN, STP and Market Maker
Market maker, STP and ECN describe where the other side of a trade comes from — and what each model changes about spreads, requotes and order handling.