To build Content management system ( CMS ) , What are the types of content that the system should be able to manage?

CMSes are typically used for enterprise content management(ECM) and web content management(WCM). An ECM facilitates collaboration in the workplace by integrating document management, digital asset management and records retention functionalities, and providing end users with role-based access to the organization's digital assets. A WCM facilitates collaborative authoring for websites. ECM software often includes a WCM publishing functionality, but ECM webpages typically remain behind the organization's firewall.     

See WordPress cms structure, and customize a theme in WordPress you can see all things that  what are content manage in WordPress system structure.