Bubble Chart is an extension of Scatter Chart. It still displays data points on a two-dimensional graph using values from two variables, but it can format the points' sizes based on a third dimension.
While Scatter Chart is useful, sometimes it is not visually interesting enough to catch the attention of your end-users. That is when the Bubble Chart comes in - to make your visualization more striking.
Exploring three dimensions at the same time can lead to interesting insights. For example, Mobiles and T-shirts are on the two extremes of the price range, but the total value they bring is roughly equal.
Creating a Bubble Chart is similar to building Scatter Chart, with the only difference of the Z-axis. This is where you put a third dimension to represent the size of the data point.
Unlike X-axis and Y-axis which discrete variables are acceptable, Z-axis only make sense with continuous variables.