Heat Map is a kind of chart that is used to show the importance of each point relative to the rest by coloring all of them according to its importance. The Chart itself looks like a table which cells are those points. Usually these points represent a value, but it’s not always so.
In this example, you can see a table which cells are filled with all hold cards combinations in Texas Hold’em poker. All cells are colored differently from light blue to strong magenta depending on chances to win with those combinations. You can notice that each column and each row represents a card from 2 to A. So, in the right bottom corner we’ve got a combination of two “2” cards and in the left top corner there is a combination of two “A” cards. Looking at this diagonal we can say that we’ve got more chances to win if our hold cards combination consists of the same cards, and the higher the card position is, the more our chances grow. Now, pay your attention on other cells; note that there are indexes written next to each combination. These indexes have special meaning for the game: “s” means that both cards are of the same suit, and “u” has the opposite meaning.
Axes are turned off as they are not necessary here, but the legend is enabled. It shows the gradation of win probabilities, and can be used to manage the Heat Map performance by clicking and hovering the legend items – first will select all points that belong to the range, represented by the legend item, and the second will highlight the same.