An easement appurtenant is when an easement runs with one parcel of land but benefits another. The parcel that benefits is called the dominant tenement, or the dominant estate, and the other parcel on which the easement exists is called the servient tenement, or sometimes the servient estate.
Imagine you own a vacation property with access to a public beach and the only way to access the beach is by crossing through your property. In this situation, an easement appurtenant would be created to give the other residents in that community the legal right to cross your property to access the beach.
Your property is the servient tenement since it’s burdened by an easement, and the beach is the dominant tenement since it benefits from the easement.