I have created a Postman collection to Access SPO using REST API.
https://github.com/pankajsurti/Access-SharePoint-Online-using-Postman
More details are here
http://www.ktskumar.com/2017/01/access-sharepoint-online-using-postman/
Refer
Refer
Understanding SharePoint’s REST and Search API Part 1 – Selecting Items
(SHAREPOINT REST WALL PAPER)
https://www.microsoft.com/en-us/download/details.aspx?id=41147
https://www.microsoft.com/en-us/download/details.aspx?id=41147
Pankaj Surti's Blog 