What's the difference between a pleural effusion and and a pleural infiltrate?

Location: Plural effusion is free fluid in the plural space , which you can actually tap it and remove as seen in the picture. , infltrates are small areas of collection in the lung tissue seen in x ray of chest due to various causes.

Fluid or not: A pleural effusion is a collection of fluid inside the chest, around the lung. A pleural based infiltrate implies a process within the lung itself, adjacent to the pleura - the lining on the inside of the chest wall and on the surface of the lung. The infiltrate could be a type of infection or possibly a cancer.