From a historical perspective 3PAR supports multiple ways to present a VLUN although "host sees" tends to be the default these days. Each VLUN template establishes the connection rule for a given set of VLUN's and multiple VLUN's can share a rule, hence more VLUN's than templates.
From the concepts guide
http://goo.gl/Z8Uf6r"A VLUN template sets up an association between a virtual volume and a LUN-host , LUN-port , or LUN-host-port combination by establishing the export rule, or the manner in which the volume is exported. A VLUN template enables the export of a virtual volume as a VLUN to hosts. Those volume exports, which are seen as LUNs by the hosts, are active VLUNs. A VLUN template can be one of the following types:
* Host sees allows only a specific host to see a volume.
* Host set allows any host that is a member of the host set to see a volume.
* Port presents allows any host on a specific port to see the volume.
* Matched set allows only a specific host on a specific port to see the volume."
