My husband's grandparent might have empyema. what is it?

Infection: Empyema (to be distinguished from emphysema) is an infection in the space around the lung, known as the pleural cavity. It has to be drained in order to be treated, and the sooner the better. Antibiotics are a distant second place in terms of importance to treating emphysema. By far, the priority is to drain the space, and this often requires surgery.

Pus around lung: The lungs are surrounded by two thin tissue layers called pleura. There is a potential space between these layers which can accumulate fluid which may be infected, or inflamed in some fashion so as to attract white blood cells. When this happens it is called empyema. It may be treated with antibiotics and drainage with a needle, and sometimes require chest tube or more invasion surgically.