According to the Healthcare Information and Management Systems Society: interoperability is "the ability of health information systems to work together within and across organizational boundaries in order to advance the effective delivery of healthcare for individuals and communities." It allows different IT systems and software applications to communicate, exchange data, and use this information.

The data exchanged by these systems may be fundamentally different yet critical to the proper management of the patient.  They may be DICOM (CT and MR images) and non-DICOM (digital snapshots of a rash or ECG waveforms); micrographs from pathology; or information drawn from patient histories – vital signs, such as blood pressure; patient allergies; or a list of medications.

With its emphasis on information systems, this common definition, however,  leaves out the most  important element of a healthcare system – people – the doctors, nurses, and staff who administer care.

To help patients, information exchanged among IT systems must be readily accessible by staff.