project database
Each Archibus project has a database with project data (such as your particular buildings) and schema data (such as the entries on the Navigator or the settings for fields).
When a user connects to Archibus, they access this database and Archibus operates according to the settings of the schema tables within the project database. For example, if you had edited a field title of the Archibus Fields schema table, this field will appear according to your edit.
If you have multiple projects (and project databases), you can transfer your project data and schema settings between project databases using the Database Update Wizard.