This note provides background on the www-factoring project, which was started in the fall of 1995. Factoring a positive integer ri means finding two positive integers u and v such that the product of u and v equals ri, and such that both u a.nd v are greater than 1. Such u and v are called factors (or divisors) of ii, and n = u v is called a factorization of n. Positive integers that ca.n be fa...