The PMI’s PMBOK describes initiating, then planning a project. During the initiating phase the project objectives are pretty much defined. During the planning phase they become more refined, but basically you are expected to know what you are doing. I am not an expert but I understand PRINCE2 takes a more iterative approach to defining the outcomes, but essentially also expects your project team to have a clear goal.
If you are a project team and someone comes to you with a brief you’ll still need to test it out and make sure you and the client are thinking about the same thing, but basically you are now ready to go.
In these projects you are typically working to a brief, a requirements specification or a design. You take the plan and break down the work then hand it to the experts and off they go. Testing and verification are against the written document and people have a good ability to validate their own work as they go. Testers don't need to speak to the client - they work off a plan or specification doc.
The whole focus of the project manager in this type of project is on optimising the performance of the team. If team members don't get what the project is about it's the PM's job to help them understand. If people are having problems getting their work done to time/cost/quality the PM takes action.
Some attributes of this type of project are described below.
Important things in this mix are work breakdown structures, a rigorous planning phase, a big requirements specification, thought out scheduling, earned value management, managing the gantt chart (or burndown chart) and of course, making sure you have a good team.
When you build whatever it is you are building you know when you are done. You can then hand over the end product, get paid and move on to the next job.
But what if you or your client aren't so sure about what you want?