The depth chart is a graphical representation of the order book. It visualizes the present supply and demand of a cryptocurrency on the market. The x-axis displays prices, and the y-axis shows the total of coins/tokens from all submitted orders up to that price. The graph is split into two sections: bids on the left and asks on the right.
On the bid size, you should pay attention to the graph from right to left. At each price level, you can see how many coins/tokens you would be able to sell at or above this price. On the ask size, you look at the graph from left to right. At each price level, you can see how many coins/tokens you would be able to buy at or below this price level.