An earthworm is a small, legless, tube-shaped animal that lives in soil. Gardeners are familiar with earthworms, which are common in healthy garden dirt.
Earthworms are not only happy to burrow in the dirt of your garden, they're also incredibly useful — they improve the fertility of soil by converting its organic matter to humus, which helps plants grow. The burrowing of an earthworm is also good for the soil's structure, introducing small tunnels that allow it to drain and air to circulate throughout. They may not be pretty, but earthworms are very helpful.