what does chr$ mean in this code

Sub rick()
Dim strabc(1 To 26) As String
Dim i As Integer
Dim strprompt As String
For i = 1 To 26
strabc(i) = Chr$(i + 64)
Next i
strprompt = "hey:" & vbCrLf
For i = 1 To 26
strprompt = strprompt & strabc(i)
Next i
MsgBox strprompt


End Sub