In Google App Engine, what is the difference between entity key and key name?

Question

And, while I know I can set the key name, can I set the entity key? Or can that only be assigned by the server?

Answer 1

Entity key is a unique key, which includes the entity key of any parent.

The key name is a name that may be assigned, but is not necessarily unique in the datastore.

Answer 2

The key is a data structure encompassing the id or name of the entity, its kind (by default, the name of the model class), and the (kind, id_or_name) information on all its ancestors (if any). The key name is only one field of this class - albeit the one you can set.