Tanning beds vs the sun

Tanning beds emit both UVA and UVB radiation.
UVA rays are responsible for tanning and skin aging.

UVA penetrate deeper into the skin and contribute to a tan.

UVB rays are primarily responsible for sunburn and vitamin D production. They have a shorter wavelength and are more easily absorbed by the skin.
The ratio of UVA to UVB in tanning beds can vary, but typically there is a higher proportion of UVA rays. UVA rays are more effective at producing a tan without causing excessive sunburn.