Springtails have other names such as collembola or snowfleas. There are many species, and they are found in environments from Antarctica to the tropics. The one thing all their environments have in common is moisture. They must have moisture to live, grow, and reproduce. Usually they will stay in the soil, leaf litter and plants outside your house, but on occasion, often in spring when their environment becomes dry, or their populations increase, they invade buildings through foundation cracks, windows, and door openings. They may also be brought into the home in potted plants. They will tend to congregate where there is moisture, or where they are trapped and can crawl no further. Springtails are generally harmless, but have been reported to cause itching and a mild allergic response in sensitive persons. I suspect just seeing them in the house may cause some persons to itch!
Infestations can be controlled with a vacuum cleaner, and/or any common home use insecticide. Try to find where they are coming in and spray an insecticidal barrier across the bottom of the door or window or baseboard. Treat the outside of the house around entry points as well.