I try to do something everyday of the week even if it's just quick home workouts. As for full on gym sessions I do at least 5 days. If your a begginer and trying to get results you could do a 4 day split, so your body can get the rest it needs to grow.
It depends a lot on how intense the workouts you do are and how much you vary between the muscles groups you work on, so just listen to your body.
The danger is, beginners do too much to get fast results. But even when your muscles grow, your bones, bowstrings, ribbons and also your fascias have to adapt. This can take up to one year. If you overdo, you risk injuries. Many workouts in magazines/dvd are intensive. Andif you do HIT or HIIT and work on all muscle groups, these rest days are important,
If you also do moderate workouts and get enough rest, it's ok to do more. Listen to your body!