The height of theses curves show daily confirmed cases and the width shows cumulative totals over time. The fact that daily cases rise and fall over time is what is meant by a (bell-shaped) epidemic curve. But the fact that cases are only "confirmed" when tested means confirmed cases are a very misleading approximation of how many people are infected.
Daily confirmed cases per million rise fast at the start largely because testing was confined to very sick people (dark red line).
Daily confirmed cases per million likewise fall fast when testing expands enough to include people who may or may not be sick (blue line). When news reports more cases we have to be careful that it is not simply more testing, or more-focused testing of groups suspected to being at risk, such as nursing homes or meat processing plants.
Headlines about a seemingly large number of confirmed cases in a particular place on a particular day are meaningless without knowing if there were more tests, and if the ratio of positive tests to the number of tests is trending up or down over periods of at least a week (7 days).
The fact that more testing has always and everywhere reduced the ratio of confirmed cases to population suggests the number of confirmed cases greatly understates how many are infected - particularly in the past when tests were rare except for people with fever and symptoms being admitted to a hospital.
This is just more evidence that we need to focus on changes that are significant (as a % of population) and sustained (weeks not days) in hospitalizations and deaths, rather daily news about either daily or cumulative confirmed cases.