Solariums are devices that emit UV radiation, similar to the one that comes from the Sun, in order to induce an increase of melanin production. They have serval modes fitted for the different types of skin as well as a timer, so it turns itself off after a set amount of time, avoiding burns while turning it off.
The main differences come from, one side, due the possibility of regulation of the UV rays, and from the other, the several relations between the mix of UV-A and UV-B.
With UV-A irradiation, the tan is more superficial, fading soon after, with UV-B you get a longer lasting tan. However the effect of UV-B is only visible only a few days after the visit to the Solarium. This way, to achieve the pretended tan intensity, when picking a Solarium the used technique in the tanning chamber should be taken into account.