Oligochaeta is a class of segmented worms within the phylum Annelida, which includes familiar species like earthworms. These organisms are characterized by their cylindrical bodies, which are divided into segments, and they play a crucial role in soil health and aeration. Oligochaetes are primarily found in freshwater and terrestrial environments. They are known for their ability to decompose organic matter, enriching the soil with nutrients. Their presence is vital for maintaining ecological balance, making them important indicators of soil quality and health.