What does source control mean?

Source control is a term used to describe measures (e.g., cloth face coverings or face shields) intended to prevent people with COVID-19 from spreading the disease to others. COVID-19 is spread through droplets produced when an infected person coughs, sneezes, or talks. Evidence suggests that people who have mild symptoms or no symptoms can spread it to others without realizing they are infected. Cloth face coverings and face shields are types of source control that provide a barrier between droplets produced from a potentially infected person and other people, reducing the likelihood of transmitting the virus.