This is one of the best visualizations I have ever seen to show how viral outbreaks work. The Washington Post offers a simulator that randomly depicts an outbreak in a town of 200 and provides four different scenarios.
Below are screenshots I took of some of the results generated. The grey blue section represents people that have not been exposed, while orange are currently sick and purple are those recovered with immunity.
Scenario 1: No social distancing or measures.
You can see the discouraging peak in orange and then a trend downward with the herd immunity being developed the fastest in this situation. Any peak in orange above what the healthcare system can handle is what we are trying to avoid.
Scenario 2: Quarantine the impacted areas and people to slow down the spread.
This has a much lower peak, but it drags out the recovery and herd immunity process a bit longer. By the end of the simulation, 15.5% of the population is still sick (vs. 1% in the first scenario).
Scenario 3: Social distancing with 3 out of 4 people practicing it.
This lowers the peak dramatically, and drags out the process dramatically. Over half have recovered by the end of the simulation (cutting R0 rate in half). One quarter of people are still at risk at the end of the simulation for when controls are released or the next season of the virus ensues.
Scenario 4: This is basically a full lockdown. This scenario only allows 1 in 8 people to move.
In this scenario, the outbreak has barely started when the simulation is over. When people resume life, the outbreak will flare up again on the 68% who have never had the virus. The R0 level will be lower from the peak of Scenario 1 when life resumes, so the second outbreak will not be quite as intense as Scenario 1, but the economic damage would be staggering under this model. The crisis is dragged out without allowing herd immunity to develop.
Scenario 1 can cause many unnecessary deaths and Scenario 4 will cause many unnecessary deaths as well as causing staggering economic damage. Somewhere in the 2-3 range is where we want to be.
These simulations are very basic and do not account for deaths (natural or due to the virus), births, travel, diminishing antibodies over time, a virus morphing over time, etc. but they still show the basic concept visually as well as anything I have seen. Please go check it out for yourselves!
Stay safe, stay strong!