MapEntity in Hammer is a type of <see cref="T:Editor.MapDoc.MapNode" /> that has a set of key/value pairs. The keyvalues represent the authoritative state of the entity. Entities may have helpers that enhance the presentation and sometimes modification of those keyvalues. The helpers may come and go; it should always be possible to recreate the helpers from the parent entity's keyvalues. Entities may also have zero or more <see cref="T:Editor.MapDoc.MapMesh" /> children.