The religious prohibitions are: no fire, no work, no entertainment or pleasure, no travelling. Everybody is to stay at home and is not allowed to come out in the streets, there are actual government officials that patrol the streets to make sure that no one is outside. Exceptions of course for emergencies.
After the Nyepi there is a day that is called Ngembak Geni, it is a day for forgiveness, everybody gets out of the house to visit relatives and friends and share the happiness of the New Year with clean spirits. And they are received with cakes and sweets that are prepared especially for this day.