powershell - What does %{ $_.Key1 } mean? -

while programming hdinsight came across lines like

$storageaccountkey = get-azurermstorageaccountkey      -resourcegroupname $resourcegroupname      -name $storageaccountname      |  %{ $_.key1 } 

i understand $_ refers result of get-azurermstorageaccountkey command. meaning of %{} ?

%{ $_.key1 } ↔ foreach-object { write-output $_.key1 } ↔ each object in pipeline, echo value of property key1.

% alias foreach-object. $_ current object automatic variable.