This is a visual orderbook and shows where resting (limit) orders are, the brighter the white the higher value the order is, the more blue to colour the lower the blue. If price pierces through the colour it means the order has been filled, however orders can also be removed in which case the colour will disappear before price touches it (what happened in this case)
As most of you will know most of the ‘whales’ trade on bitfinex, and this specific pictures I’ve sent are from the bitfinex orderbooks. The same whale who purchased over 1600 coins from the prices between 37.5k down to 34.5 has taken profit from 45k-48k and had successfully rebought between 43.8k-40k. This type of orders are referred to as ‘Iceberg orders’
However his remaining orders that remained unfilled from lower prices from the Ukraine invasion dip, he has now pulled from the market. These orders combine at over 1,000+ BTC total.