Whats a Security Graph?

So whats a security graph?   " ... Data visualization is a booming segment of the big data job market, and it’s found an obvious foothold in security. The requirement of data visualization in job descriptions has increased in big data jobs by 12 percent in just the first half of 2015, which may indicate the skill is in the early stages of demand. As more companies begin to realize their need for quick digestions of large volumes of data to find trends, especially in security, the demand for visualization will likely keep increasing, vague as the description may be ... "