Advanced Integration Services are available in IBM BPM Advanced version and provide means to implement an integration via IBM Integration designer. AIS is initiated in Process Designer by creating a implementation of type AIS as shown in this image
Then you define its input and output parameters, now you can open it in IID with a launch button available in Process Designer overview page for AIS, or alternatively from IID you can connect to the process app and it will show up as ready to implement, you can implement an AIS as a microflow, long running BPEL or a simple Java implementation. Once implemented and committed to Process Center when you invoke the AIS in Process Designer the input data is sent over to it and the implementation executes and returns the data back to the Process Designer similar to any other Integration we have, difference being that the implemenation is in IID side and utilizes all the features of IID, an alternative approach is to create the implementations directly in IID and expose them as web services and consume as any other web service in Process Designer side, this removes the need for an AIS.