A dwelling is a human building, such as a house or Taipei 101. In accordance to the magical laws that Frond established after the fairies retreated underground, any fairies that enter a dwelling without permission would succumb to severe vomiting and nausea, and eventually lose their magic. This rule is referred to as the Rule of Dwelling.
In the first book Artemis is able to keep Holly in his house by telling her it is against his wishes for her to attempt to leave his house.
“We are both fully aware of the rules here, Captain. This is my house. You must abide by my wishes. Your laws, not mine. Obviously my wishes do not include bodily harm to myself, or your attempting to leave this house.”
However even though Artemis told Holly his wishes do not include bodily harm to himself; Holly is able to whack Artemis right on the nose with no ill effects.