If only two elements (two words, two phrases, two clauses) are joined by a coordinate conjunction, no comma is needed before the conjunction:
Il a dit qu'il était fatigué et qu'il
rentrait chez lui.
(He said that he was tired and [he] was going home.)
If three or more units are joined, commas separate them:
Hommes,
femmes, et enfants sont bienvenus.
(Men, women, and children are welcome.)
or
(Men, women and children are welcome.)
English allows both ways.
See Also: