A Partner Service Provider is a participant Web service that is used in building an invoke activity. It consists of a name and an interface.
You can create a partner service provider in stages:
Enter a name or accept the default name, Provider.
If interface resources are available, you can select the interface. If they are not, you can add them later, in the Properties view
When you complete the participant details, you are essentially creating all the elements needed for a process' invoke activity.