A component exposes your pages to peoplesoft only.Moreover it helps us to define common properties for a set of related pages.
A component interface is a set of application programming interfaces (APIs) that you can use to access and modify PeopleSoft database information programmatically. PeopleSoft Component Interfaces expose a PeopleSoft component (a set of pages grouped for a business purpose) for synchronous access from another application (PeopleCode Java C/C++ or Component Object Model [COM]).