The gap between the highest bid price and the lowest ask price on the order book. It's a market maker's primary source of profit, and also a hidden cost that traders bear directly — even ignoring the fee schedule entirely, the simple fact of "buying slightly higher, selling slightly lower" is itself a cost.

Exchanges tier users based on how much identity documentation they've submitted, with higher tiers unlocking larger daily withdrawal limits and access to more trading products — it's not a binary verified-or-not choice, but a ladder of how deep the verification goes.

A fee structure where exchanges charge different rates based on whether an order adds or removes liquidity: makers who place resting limit orders pay lower fees, while takers who fill existing orders pay higher fees.

A professional firm that continuously posts limit orders on both the buy and sell sides, essentially selling the service of "someone is always available to trade with you." It profits from the bid-ask spread, exchange rebates, and OTC trading fees, and stays directionally neutral, without a particular preference for price going up or down.

The cumulative volume of resting buy and sell orders stacked at various price levels on the order book — a larger volume means the market can absorb bigger trades without significantly moving the price, while a smaller volume means even a modest order can push the price noticeably.

A compound order made of two prices — a stop (trigger) price and a limit price. Once the market hits the trigger price, the system automatically fires off a limit order, not a market order, to protect against slippage from a market order during sharp moves — at the cost that this limit order can itself fail to fill entirely if price runs past it too fast.

A trading pattern where the same party (or colluding parties) simultaneously act as both buyer and seller, generating trade records that look genuine but involve no real transfer of ownership, with the goal of faking trading volume or inflating price to mislead other traders about genuine market demand.