express home delivery service; courier service
Refers to the service itself, such as those provided by Yamato Transport or Sagawa Express.
宅配便で荷物を送ります。
I'll send the package by courier service.
express home delivery parcel; courier package
Refers to the physical parcel or box sent via such a service.
宅配便が届きました。
A courier package has arrived.
I sent my friend some homemade cookies by courier.
A courier parcel just arrived, so it's sitting by the front door.
My mother received the courier parcel on my behalf.
It's convenient to use a courier service for large parcels.