Order book

Bids sit below the current price, asks sit above it, and the gap between the highest bid and the lowest ask is the spread. Depth further down the book (more orders at nearby prices) makes it easier to trade larger amounts without moving the price much.

For example, if the top bid is $59,980 and the top ask is $60,020, the spread is $40. A market buy order fills against the asks starting at $60,020 and works its way up the book until the full order size is filled.

A common mistake is assuming the price you see on a chart is the price you'll actually pay. That headline price is usually just the last trade — your real fill price depends on how much depth sits at each level of the order book.