The brackets are used to signify that the text is a variable or identifier and not a type or some other keyword.
For example, I can do something like this if I wanted to:
Private Sub ReceivedText(ByVal [String] As String) 'input from ReadExisting
If Me.lblStatus.InvokeRequired Then
Dim x As New SetTextCallback(AddressOf ReceivedText)
Me.Invoke(x, New Object() {([String])})
Else
Me.lblStatus.Text &= [String] 'append text
End If
End Sub
Without the brackets Visual Studio (for example) will think that 'String' is a type and give you the error: "Keyword is not valid as in identifier". What to actually name identifiers or variables is a whole other question.
