Shows use of 2 google tools - looks intriguing. Wonder Wheel gives you a visual picture of relationships or subsets of the term you searched; you can then search on the subsets of interest. Timeline arranges links in order, from oldest to newest, and shows a frequency distribution of the links, over time. This includes ancient (pre-internet) information, if it's coded with a publication date.

From Diigo's website, an overview of the features and uses of Diigo.