AHAs (alpha hydroxy acids) and BHAs (beta hydroxy acids) both work to exfoliate the top layer of dead skin cells. BHAs are often used in blemish or pore-minimizing products.
The SPF number — or sun protection factor — refers to the length of time you can spend in the sun without burning. That means, for example, if you wear an SPF 15 lotion, your skin should be protected from burning about 15 times longer than without any lotion. The exact length of time will vary by your skin tone & genetic makeup.
Self-tanners do not protect skin from damage caused by sun exposure unless they contain SPF protection, so it is important to still wear a lotion with broad spectrum SPF protection — even if you self-tan.
Skincare products containing AHAs (such as glycolic acid) or BHAs (such as salicylic acid) help exfoliate the top layer of dead skin cells to reveal more radiant skin underneath. Skin scrubs work similarly by mechanically removing the top layer of dead skin cells.