You mean the -Property parameter on the Get-View cmdlet?
Normally the Get-View cmdlets returns the object(s) with values for all properties of each object.
If you only need a specific property, you can specify it on this parameter.
The fewer properties the faster the Get-View cmdlet will be, especially in bigger environments.
For example the following will return all VirtualMachine objects, but only the Name property will have a value.
Get-View -ViewType VirtualMachine -Property Name