What are alpha- or beta- hydroxy lotions?

I read that this can help keratosis pilaris but i don't know what it is. What are some brands that are good for this?What are alpha- or beta- hydroxy lotions?
They are acid skin care products. One product you might want to invest in would be the ';Earth Science A/B Hydroxy Acid Night Rejuvenator (1 fl oz).';