In 1982 a polynomial-time algorithm for factoring polynomials in one variable with rational coefficients was published (see A.K. Lenstra, H.W. Lenstra, Jr. and L. Lovasz, Math. Ann., vol.261, p.515-34, 1982). This L³-algorithm came as a rather big surprise: hardly anybody expected that the problem allowed solution in polynomial time. The purpose of this note is to present an informal description of the L³-algorithm