Most crypto trading happens on order books: a list of what people will pay and what they'll accept. Buyers post bids, sellers post asks, and a trade happens only when one meets the other.
Reading the ladder
The highest bid and the lowest ask form the inside of the book, and the gap between them is the spread. Orders at the same price are usually filled in the order they arrived, which is why being first in the queue is worth something to professional traders.
The ladder shows the sizes waiting at each price. Green bars are bids, red are asks, and the middle column is the price itself.
What moves the price
A price moves when an order is big enough to eat everything at the inside level, or when traders simply pull their orders. The two look identical on a price chart, and quite different on the book.