What is humus what is the role of earthworm in increasing the quality of humus

Humus contains decomposed remains of plants and animals. Humus is rich in organic content and thus makes soil fertile.

Earth worms increase the quality of soil because when they burrow into soil they make it lose. Hence increasing water holding capacity.  Also, earth worms ingest soil and organic matter and cast undigested material. This cast consists of finer soil and radially available organic material which can be taken up by the plants. Thus earth worms increases the rate of formation of humus.