Imagine there are two mountains. On one mountain, hundreds of thousands of medical and health researchers produce new knowledge and publish their results, in an estimated two million new research articles a year.
Dissemination is the communication activity designed to bridge the gap between the two mountains.
Traditionally, there has been massive funding to support medical and health research, and some funding for public relations programs to make people aware the research has been done, but there has been very little funding for activity to strategically communicate the results to people who can use the information, and help them apply it appropriately. That is one reason, among many, for some huge gaps between what we know from research, and what we practice in health-care. This is the business of dissemination.