Business partners who use usage type Process Integration (PI) can exchange messages between their system landscapes.
● If both business partners use PI, then you can connect the two Integration Servers to exchange data.
More information: Integration of Business Partners who use PI
● A PI Integration Server can also send and receive SAP XI 2.0 messages. Therefore, it is also possible to integrate business partners who use SAP XI 2.0.
More information: Integration of Business Partners who use SAP XI 2.0.
● Smaller business partners who do not use PI can use the Partner Connectivity Kit (PCK) to exchange messages with the system landscape of a business partner who uses PI.
More information: Integration of smaller Business Partners and Subsidiaries
Business partners do not necessarily have to be two different companies; they could also be two independent IT areas within a single company.