You can find projection tags in several places:
How do I set up a project tag?
You can set the tags on the project detail just below the project title:
These labels can only be seen by you and no one else. So you can rank your projects exactly as you need them.
What are the project tags good for?
Tags are good when you have a lot of projects. Typically when you are invited to many projects or have a lot of your own projects. On the All Projects page, you can turn on filters that will make your listing more transparent.
Another reason to tag your projects is the method of billing. When you invoice one client for multiple projects, you can filter your projects and select the invoices you want to bill on the Finance>Billing page. You do not have to click on all the projects individually.