What type of address does a network projector use?

Its unique address as explain by Rambabu.

Each projector on the network is identified by a unique address. You can enter the address as a Uniform Resource Locator (URL) (for example, http://server/projectors/projector_1) or as a UNC (Universal Naming Convention) path (for example, \\server\projectors\projector_1). Your system administrator may be able to provide you with the address of a specific projector.

The address is displayed on the projection screen when a presentation is not in progress. If you're using a security-enabled projector, the projector password is also displayed.
http://windows.microsoft.com/en-IN/windows-vista/Network-projectors-frequently-asked-questions

unique address