It refers to all persons/expertise/budget resources needed to implement the project. It depends on the dimension of the company, of course.
For example, to implement the project and verify all risks it can be the DPO, the IT Manager, and the Head of the Legal Department, but of course, if you need to implement a Teleworking policy you may also need the HR manager. Or to mitigate the risks you need to buy new software/hardware.
When implementing the GDPR project you need to take into account all these elements before starting.
To know more about how to start implementing GDPR, here you can find a 9 step procedure: