Ashwagandha is an evergreen shrub that grows in Asia and Africa. It is commonly used for stress. There is little evidence for its use as an "adaptogen."
Ashwagandha contains chemicals that might help calm the brain, reduce swelling, lower blood pressure, and alter the immune system.
Since ashwagandha is traditionally used as an adaptogen, it is used for many conditions related to stress. Adaptogens are believed to help the body resist physical and mental stress. Some of the conditions it is used for include insomnia, aging, anxiety and many others, but there is no good scientific evidence to support most of these uses. There is also no good evidence to support using ashwagandha for COVID-19.