Heatmap
It is a graphical representation of data where the individual values are represented as colors.
It needs self-explanatory colors, for example if our data is made of temperatures, we can use blue if the value is low and red if higher. We all associate blue with cold and red with hot.
Color gradient
It specifies a range of color wich depend from the position. In the image the position from left to right represent the values from minimum to maximum.
Green to White to Red
Usually everyone associates green to good values and red to bad ones. This color gradient maps lowest values to green, medium ones to white and the highest ones to red.
Blue to White to Red
Usually everyone associates blue to low values and red to higher ones. This color gradient does what we expect: maps lowest values to blue, medium ones to white and the highest ones to red.
Blue to Red
As the ones before but has no white, this means intermediate values get mapped to an intermediate value but darker than both red and blue.
Hue Gradient
This Gradient uses a wider range of colors, this allows more precision in mapping a value but an harder readability when it's printed B/W (black and white). The gradient in the image uses Hue values from 0° to 240°.
