Springtails are very small, wingless insects. Some are brown or gray, while other are brightly colored. They have a structure (furcula) on their underside that enables them to jump.
Springtails are probably the most abundant non-social insect on the planet. There are approximately 650 species in the United States alone and they are found in both the Arctic and Antarctic. They can be very common in damp, organic soil where they feed on fungus. Large numbers in any area will show that the soil is healthy. They rarely cause any damage to plants, but will occasionally feed on young shoots. One species, the garden springtail (Bourletiella hortensis), is a potential pest in some situations including in houseplants. Occasionally they wander into homes and because they can jump, they are frequently mistaken for fleas. They require moisture, so if you have springtails in your home, you may have a moisture problem.
Contrary to what some people believe, springtails are not capable of infesting human beings. This is a myth that is often found on the internet.