Diigo is a social annotation tool. It is in the same category with the “older” Delicious (https://del.icio.us/)
But also in competition with a tool we know now well: Evernote.
In 2014, it was predicted (as with Evernote) that other tools, such as SlideVibe:
may take over Diigo, but the latter still goes strong. Here are two short video intros to the use of features of Diigo:
Note that as with Evernote, Diigo is not only a specific tools for performing specific tasks (in this case bookmarking).
As with Facebook, YouTube and most social media tools, Diigo is a social tool: you can share your bookmarks on different levels and collaborate and express your creativity by organizing and sharing your collected information