A project can be what suits you best: an event, the redesign of a site, the monthly edition of your internal magazine.
Do I have to create the content or the project first?
There are several way of doing on this subject and it will be according to what suits you best with your teams. The first strategy would be to create a project and qualify it (write its brief, assign leaders to it, indicate its degree of priority, etc.).
Then, thanks to the comments, you will be able to question and invite members of the team on this space and assign contents to them to produce.
As you can link files without any size limit (press kit, high definition videos, etc…) on this project, the various editors can use them to produce content within their responsibilities.
Thus, all the information related to a project is located in one and the same place. You no longer repeat the same instructions over and over again in various meetings.