Meaning Of Bracket Notation

The following code was posted in another thread:

Private Sub UserForm_Initialize()
Dim a, v, x, ws As Worksheet
Set ws = Sheets("Scheduled Courses")
a = ws. Range("a2", ws.[a65536].End(xlUp)).Value
With CreateObject("scripting.dictionary")
For Each v In a
If Not IsEmpty(v) And Not .exists(v) Then
.Add v, Nothing
End If
Next
x = .keys
End With
With Me.ComboBox1
.Clear ' clear the listbox content
.List = x
.ListIndex = 0 ' select the first item
End With
End Sub

How are the brackets used in the 4th line? I have not seen this notation before. Is this some kind of a shorthand for a Range("A65536") reference?