Excerpts from "How to Get Started with Office Delve" by Oliver Bartholdson, 2/10/15 (https://newsignature.com/articles/how-to-use-office-delve)
What is Microsoft Office Delve?
Delve is a powerful search engine that gives you what you need even before you ask. It looks across all of the content in your organization, checks to make sure you have access to it, and then presents it to you in a smart and intuitive interface. It is powered by the Office Graph, which uses machine learning techniques to map all of the activities taking place across email, OneDrive for Business, SharePoint Online and Yammer.
Where are all of my documents?
To start seeing items in your Delve feed, you need to store documents in SharePoint Online and OneDrive for Business. If you are not seeing a lot of content in Delve, chances are it is because you have not started storing all of your personal files in OneDrive for Business, and your shared files in SharePoint Online Team Sites.
Since Delve is built upon the relationships and connections made between people and files, it is critical that your teams are making documents available to their peers by sharing the content. An employee will only see another employee's document in Delve if they have access to it in either Team Sites or OneDrive for Business.
Delve has the power to change the way you find information. Instead of having to find a document based on its filename and sorting through pages of search results, it presents you with documents that are important to you and your team. Delve is an exciting new addition to the Office 365 family, and I am excited to see how it and Office Graph transform the way we work.