Sun Protection Factor or SPF: 

A scale for rating the level of sunburn protection in sunscreen products. The higher the SPF, the more sunburn protection it provides. Sunscreens with an SPF value of 2 through 11 provide minimal protection against sunburns. Sunscreens with an SPF of 12 through 29 provide moderate protection, which is adequate for most people. Those with an SPF of 30 or higher provide high protection against sunburn and are sometimes recommended for people who are highly sensitive to the sun.