"Toggle" means to switch between to states (on/off, yes/no, in/out, show/hide, etc).
A Further Practice section is an area to practice what you have learned. Here, you are provided with a suggestion of what you could do. The suggestion is to replace "else" with "elseif". This creates the opportunity to test a second condition, doDisplay. Follow the same steps you used to create the first condition, doPlot.