Data Management is the process by which you control your data. For research data, it's knowing what you have, where and how you got it, annotating and documenting it, keeping it secure and intact, sharing it, getting credit for sharing, and/or preserving it in an archive. The lifecycle below shows one potential workflow. Image courtesy of http://data.library.virginia.edu/data-management/
Researchers manage their data in order to:
For examples of what happens when data is not managed correctly, Retraction Watch details many cases.