What is alpha/beta hydroxy?

I've been wondering this for some time, as 2 of the cleansers I use contain beta and alpha hydroxy. Turns out, beta hydroxy is just another name for salicylic acid. Here's some other info I found interesting:

Alpha and beta hydroxy acids are derived from apples, ginger, oranges, grapefruit, sugarcane or willow bark, and will gradually peel off the top layers of dead skin and minimize wrinkles.

The Alpha's (AHA): One of the alpha hydroxy acids found in cane sugar, sugar beets and unripe grapes, glycolic acid, is an odorless, crystalline compound used to control the acid/alkali balance and also as an exfoliant, It works easily into the skin to break up, and remove, bonds of dead skin cells.It has been said that loosening these bonds stimulates the body's built-in dead-cell elimination, or sloughing off, process, making way for new skin cells to emerge and for fine lines to be smoothed over. The use of these alpha hydroxy acids has also been shown to reduce skin discoloration and to even out pigmentation.

The Beta's (BHA): Salicylic, benzoic and buteric acids -- all beta hydroxy acids -- are also reported to be excellent exfoliators, and are often combined with alpha hydroxy acids for their synergistic, complementary activities.

The "hydroxys" have also been shown to help those with oily and acne-plagued skin, since dead skin cells are no longer able to clump up around hair follicles and compromise the natural drainage of the oil-secreting (sebaceous) glands.Citric acid is another hydroxy powerhouse, one extracted from citrus fruits. These fruits are rich in vitamin C and bioflavonoids, including rutin, which are said to strengthen the small capillaries that provide nourishment to the skin.

The main difference between alpha hydroxy acids and beta hydroxy acid is their lipid (oil) solubility. Alpha hydroxy acids are water soluble only, while beta hydroxy acid is lipid (oil) soluble. This means that beta hydroxy acid is able to penetrate into the pore which contains sebum and exfoliate the dead skin cells that are built up inside the pore. Because of this difference in properties, beta hydroxy acid is better used on oily skin with blackheads and whiteheads. Alpha hydroxy acids are better used on thickened, sun-damaged skin where breakouts are not a problem.

Examples:
Neutrogena Deep Clean Gentle Scrub contains BHA.
Neutrogena Healthy Skin Anti-wrinkle Anti-blemish scrub containts AHA.

source:
http://findarticles.com/p/articles/mi_m0FKA/is_n4_v58/ai_18178328/
http://dermatology.about.com/cs/skincareproducts/a/aha_2.htm