Bubble charts display correlations between three variables, x, y, and z. They're an extension of the scatter plot, which displays correlations between just two variables. x = first variable, shown on the x-axis y = second variable, shown on the y-axis z = third variable, represented by the bubble's size or area
https://depictdatastudio.com/charts/bubble/
Example 1
Example 2
Source: buzzfeednews