Delve is a new addition to the Office 365 offering from Microsoft. It was called as Oslo earlier and was designed to enhance the Search experience of the users.
Delve helps you discover the information that's likely to be most interesting to you right now - across Office 365.
The more you and your colleagues work together, by viewing, editing and sharing each other's documents, the more useful Delve will be for all of you.
Delve learns from how you and your colleagues work, and tailors the information to each of you. What you see in your views in Delve is different from what your colleagues see in theirs.
You don't have to remember the title of a document or where it's stored. Delve shows you documents no matter where they are stored in OneDrive for Business or in Sites in Office 365.
Delve never changes any permissions, so you'll only see documents that you already have access to. Other people will not see your private documents, for example documents that you've stored in private folders in OneDrive for Business.