Help with "" Two double quotes - understanding

I have tried to find any explanation of the "" in a script

http://vblog.strutt.org.uk/2011/07/lun-ids-of-esx-datastores/

The snippet of code is

    foreach ($UUID in $UUIDs) {
        $Lun = $ScsiLuns | ? { $_.UUID -eq $UUID.UUID } | Select -first 1
        $objVolume               = "" | Select Datastore, Make, Model, LUN

but it is the = "" | select that I am trying to get my head round. I just cannot find that syntax explanation. Can someone refer me to somewhere?

Thanks.