Economist article on coronavirus
R is a reference to R0, otherwise known as the basic reproductive rate, and means the number of new cases from a single patient infection. R0 has to be above 1 for a disease to persist. It is a classic equation which account for the probability of transmission against immunity. The y-axis is the number of infecteds, very poorly presented.

The idea is that R0 will be lower if there is containment (less people to infect because you can't move around), but will last longer, possibly because the number of naive patients (not encountered the virus) will be larger over a longer period of time. 

That particular graph appears to be saying that everyone at risk of infection will get infected with or without control measures (the surface area under the graphs is approximately the same*) and the only thing that will halt the virus is acquired immunity. If this is mainstream economic thinking then I beg to differ, albeit I note the source is CDC (again see note*). 

For example, all other respiratory viral infections are seasonal. If COVID-19  is seasonal containment is the right choice, because the window of transmission is limited.

*, Given this is of CDC origin I think either its a mistake, or at the very least was taken out of context, because the idea is that overall there is a lower number of people infected as a result of "social distancing" and that does not appear to be what the two curves show.