I need to find factors of the eq, but unable to understand use of mod.

> `mod`(Factor(x^5-1), 2);

                            output redirected...

> `mod`(Factor(x^5-1), 7);

            powers=  4    3      2            
                       (x  + x  + x  + x + 1) (x + 6)

> `mod`(Factor(x^5-1), 5);

                   powers=     5
                                  (x + 4)