How to properly use Select count(*) as

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VB

MS-Access

I am using an SQL Select statement in one of my programs (something I pillaged blindly from the web somewhere) but in truth I don't actually understand the statement completely and cannot seem to get an explanation anywhere (including W3Schools where I do a lot of learning)

Ssql = "SELECT Count(*) as NoOfJustifyRecs FROM Purchase_Justify WHERE PJ_Po_Number = '" & cbo_Order_Number.Text & "'"

       da = New OleDb.OleDbDataAdapter(Ssql, cn)
       da.Fill(ds, "NoOfJustifyRecs")

       cn.Close()


       If ds.Tables("NoOfJustifyRecs").Rows.Count = 0 Then
            ' do something
       End If

Could someone please explain to me the use of 'as NoOfJustifyRecs' ?
Ideally I would like to say something like

If NoOfJustifyRecs = 0 then
  '  do something
EndIf

but obviously NoOfJustifyRecs is not declared.

My big question is what is the point or use of using 'AS NoOfJustifyRecs' when as my code stands I can simply get the value from the dataset.

Thanks guys.