Project Online is a collaboration tool that can be used to save, view, and edit project plans, enter your timesheets, report your project status, and report across your portfolio of plans, all with the benefit of SharePoint. You can either install Project Pro 2013 locally or get the Project Online with Project Pro for Office 365 license. And depending on the scheduling requirements, you might be okay with using the web based planning Project Web App 2013 (PWA) has to offer.
Comparing Project Server on-premises with Project Online
This MSDN article will help you decide whether to use Project Server on-premises or Project Online, and what kinds of extensions you can develop in either case.
Compare feature availability across Project Portfolio Management offers
This TechNet article will help you decide whether Project Online portfolio management features are right for your organization.
Project Online How-to from the Office team
This article provides links you can use to browse for content about the major feature areas in Project Online.
Project Online TechNet TechCenter
Microsoft has provided administration resources you need to try Project Online including details to explore, deploy and operate PWA.