Digital History is a sub-field of the Digital Humanities. It is a loose term for any combination of the applications of technology and the study, analysis or presentation of history. At it's most complex, it can involve techniques such as data analysis concepts and text mining. Or, it can be as simple as a website.
A Digital History flash presentation from BBC. The webpage describes it as "web technology to reveal the sweep of historical forces and the rise and fall of great empires and ideas over 5000 years in a way that no book could ever do."
A great site for anyone interested in exploring the concepts of Digital History further. The site "offers novice-friendly, peer-reviewed tutorials that help humanists learn a wide range of digital tools, techniques, and workflows to facilitate their research."