A Combined Chart is one with several series of different types, usually demonstrating some related functions. Those charts use two Y-Axes or X-Axes quite often as series may demonstrate values in different scales.
This Chart uses a Column and a Line Series to show the dependency of late arrivals from the reported cause. There are six causes mentioned in the chart: Traffic, Child Care, Public Transportation, Weather, Oversleeping and Emergency. There are two Y-Axes: left one shows the delay in minutes with its value range from 0 to 184.8 and the right one shows the percent of late arrivals. The Column Chart, in its turn, demonstrates the delay time and the Line Chart uses the right Y-Axis so shows the late arrivals rate in percent.