The second line here specifies what type of data our x-axis represents. Which in this case, is a continuous time value as indicated by the Time Axis function. Notice that we call this function on the chart object return by the dimple constructor function. We could potentially have multiple charts on a single page and this allows us to specify which chart we would actually like to manipulate and add an axis to. The first argument is the axis which we would like to add, in this case, x. In the second argument, the string representing the column name of what we would like to plot on that axis in this case, the year. So this line of code says, add to my chart a time axis which will be represented by the x-axis on our chart and correspond to the year column of our data. The third line here specifies what type of data our y-axis should represent, and has an identical interface to the add time axis function. In this case, we have a continuous value we would like to plot on our y-axis specified by add measure axis. The third line says add to my chart a continuous value on the y-axis which corresponds to the attendance column of my data.