Copy File/directory using Buffer?

[tgf-47]

Can anybody please explain to me what this code will do to the copy?

Using source As New IO.FileStream("source path here", IO.FileMode.Open)
    Using target As New IO.FileStream("destination path here", IO.FileMode.Create)
        Const BUFFER_SIZE As Integer = 1024
        Dim buffer(BUFFER_SIZE - 1) As Byte
        Dim bytesRead As Integer = source.Read(buffer, 0, BUFFER_SIZE)
 
        While bytesRead > 0
            target.Write(buffer, 0, bytesRead)
            bytesRead = source.Read(buffer, 0, BUFFER_SIZE)
        End While
 
        target.Close()
    End Using
 
    source.Close()
End Using