Necrotizing fasciitis is a dangerous rapid bacterial infection of the lowermost layer of the skin tissue. At first glance it would seem that nothing has occur however in a few days you'll see reddish-purple to bluish-gray hue appearing on your skin swelling will also occur and as well be warm to the touch https://www.ncbi.nlm.nih.gov/books/NBK430756/
It essentially means rotting of the skin or flesh eating of the skin in this context
Fasciitis means the inflamation of the Fascia and Fascia is a layer of connective issue located beneath your skin https://www.webmd.com/a-to-z-guides/what-is-fascia
One can get infected by post-surgery, invasive and everyday procedure https://www.ncbi.nlm.nih.gov/books/NBK430756/ like C-sections also as well one can contract this infection during a pregancy complication and any kind of trauma related injury.
Although it is uncommon to get this infection the more at risk types of patient are the one who suffer from diabetes,kidney disease immunosuppression and obesity https://pmc.ncbi.nlm.nih.gov/articles/PMC8686767/