It means that there are other residency programs at the same institution. In practical terms, it means there is more "competition" over who is going to do procedures or see certain kinds of patients.
This is usually more of an issue for family practice programs because FP "encroaches" on a lot of other specialties, but it can be an issue with IM programs too, as far as procedures are concerned. For instance, if there is a surgery residency program and a family practice or IM program at the same institution, the surgery residents might get to place all or most the central lines or chest tubes and the IM or FP residents don't get enough/any experience in these procedures.
