Comics read from left to right, manga reads from right to left. Manga has a wider array of genres, comics is all super heroes, manga is love and life, comics are meh.
Inside Japan there's no difference. Outside of Japan people use the word to mean comics made in Japan. Sometimes it gets used for South Korean comics too because outsiders don't bother to distinguish between them. The word for South Korean comics is manhwa.
Comics read from left to right, manga reads from right to left. Manga has a wider array of genres, comics is all super heroes, manga is love and life, comics are meh.
This person almost had it but AaaaNinja is right, there's no difference. A manga is a Japanese comic. Also Comics have more than just superhero genre. There's the comedy epic, Bone, the thriller East meets West etc. etc. Marvel and DC are primarily superhero genre but they're not the only comics out there.
The biggest key difference between the two is a manga is created by one writer who(I believe) is usually the artist as well, this means when they leave, or die, the story ends with them where as comics in the western sense can be continued by other creators. So if Naruto was an American comic some new writer and artist could work on continuing the story(This can and does lead to inconsistencies though)