According to Oracle Document:

HOMOGENEOUS:

This type of execution plan extracts data from multiple instances of the same SOURCE system. For example, a BUSINESS might have an INSTANCE of Oracle EBS 11i in one location and time zone and another instance of Oracle EBS 11i in another location and time zone. In such cases, the timing of data extraction from the different instances can be staggered to meet your business requirements.

Heterogeneous:

This type of execution plan extracts data from one or more instances of dissimilar source systems. For example, a business might have an instance of Siebel 7.8 in one location, an instance of Oracle EBS 11i in another location, and a second instance of Oracle EBS 11i in yet a THIRD location. You can also stagger the timing of data extraction when you use this type of execution plan.

According to Oracle Document:

Homogeneous:

This type of execution plan extracts data from multiple instances of the same source system. For example, a business might have an instance of Oracle EBS 11i in one location and time zone and another instance of Oracle EBS 11i in another location and time zone. In such cases, the timing of data extraction from the different instances can be staggered to meet your business requirements.

Heterogeneous:

This type of execution plan extracts data from one or more instances of dissimilar source systems. For example, a business might have an instance of Siebel 7.8 in one location, an instance of Oracle EBS 11i in another location, and a second instance of Oracle EBS 11i in yet a third location. You can also stagger the timing of data extraction when you use this type of execution plan.