It helps to understand "gain of function" if you're going to read this article. Gain-of-function research is medical research that genetically alters an organism in a way that may enhance the biological functions of gene products. This may include an altered pathogenesis, transmissibility, or host range, i.e., the types of hosts that a microorganism can infect.
Of course, there is little to help us understand why anyone would want to help a virulent pathogen such as Covid gain function...