Sporangia are the structures that house the spore-forming cells. After the spore-forming cells undergo meiosis to form spores, the spores will be in the sporangia.

('Sporangium' is the singular of 'sporangia').

Each sorus contains a cluster of sporangia. You will see this more clearly in the spore dispersal movie.

Each circular brown structure is a sorus in the individual sporangia appear as brown specks.