The Land Register (in Danish: Tingbogen) is a public register which records certain rights to real property, cooperative housing, chattels, vehicles and the like.
Your right to real property in Denmark is not secure from the property being sold or subjected to security interests in contravention of your right until you have registered your right (your title deed, mortgage or easement, etc.) with the Land Register.
If you purchase real property in Denmark, you can search for the property in the Land Register to ensure that there are no rights registered on the property that you are not aware of.