During Extra Magic Hours, guests staying on site can enjoy a little more time in a certain park on certain days, either after the park has closed or before the park opens to the general public.
This is a perk only for on site guests and it is one more reason to stay at a Disney hotel rather than off site.
If you are staying off site, this can still work to your advantage. On days with Extra Magic Hours, that park tends to be busier. So I’d suggest looking at the Extra Magic Hour schedule on Disney’s website, and plan to avoid being at that park on that day.
If your staying on Disney property, I’d still recommend going to the park with the Extra Magic Hours. Even if it’s busier through the day, there’s considerably less people during those hours since the park is closed to the general public.
This is definitely a good perk for on site guests. It’s just one more reason to stay at a Disney Resort!