https://gisanddata.maps.arcgis.com/apps/opsdashboard/index.html#/bda7594740fd40299423467b48e9ecf6
On the arcgis site, compare the number of cases in mainland China vs. the number of cases in the rest of the world. Initially, the outbreak in China was exponential but they brought it under control fairly quickly and their graph has flattened. That's what is meant by "flattening the curve".
In contrast the cases in the rest of the world currently stand at around 133,000 cases but is still increasing exponentially with a period of doubling of around 4 to 5 days.
If the exponential growth is left unchecked, in two months there will be ~1 billion cases.
Do the math.