What’s the purpose of copying the projects?

[hzgui8440]

I use Enterprise PeopleTools 8.49 Installation for Oracle for a guide to install the peoplesoft. When I did the step of Updating Database to Latest PeopleTools Release of Chapter 7B, I found that it told me to copy the project to the database but no to tell me to build it. Without building the project, the objects of the project can not be built. Should I need to build the project? What’s the purpose of copying the projects?