https://i.ibb.co/yfwGbJK/jochen-hoenicke-de-queue-1.png

This picture displays the number, fee, or weight of the unconfirmed transactions, also known as the transactions in the mempool (the transactions that haven't been written to the block-chain yet and kept in the volatile memory). It gives a real-time view and shows how the mempool evolves over the time.

It provides a real time view and shows how the mempool is growing over time. Transactions are colored by the amount of fees they pay per virtual byte. Data is generated from my complete node and updated every minute. Note that in decentralized cryptocurrencies there is no global transaction mempool; each node keeps its own pool of unconfirmed transactions that it has viewed.

Every the data is separated into different charge rates which are given in satoshis per byte.
The lowest colored line is for the transaction that pays the lowest fee.
If the colored line persists for several hours without shrinking, it means that the transaction that paid this amount of fees was not confirmed during that time, because there was a transaction with a higher payout that took precedence.

The horizontal axis is time and you can choose a range from the last 2 hours to all of them.
The chart's vertical axes can be switched between amount, cost, and weight. In a weight chart, the chart height reflects the total transaction size, not the number of transactions. If the line on the weight chart is much larger than on the count chart, the trade on this line is larger than the average. Similarly, in a fee chart, the height reflects the total amount of fees paid by pending transactions.

for more information you can see it here