A bed/booth you lay/stand in. It has ultraviolet bulbs that emit UV very much similar to the sun. It will give you a tan very much like the sun does. There is a possibility skin cancer can be acquired from using one of these devices.
In efforts to get a tan by direct sun-exposure, one knowingly avoids high SPF values in order to get a darker skin-color ASAP. This usually means risking a sunburn. However, burnt skin will gradually turn tan.