What are the three basic groups of nematodes?

Nematodes can be categorized into three basic groups: free-living nematodes, which primarily inhabit soil and aquatic environments; plant-parasitic nematodes, which feed on plant roots and can cause significant agricultural damage; and animal-parasitic nematodes, which infect a variety of animals, including humans, often leading to health issues. Each group plays distinct ecological roles and has varying impacts on their environments and hosts.