WxPython Bind events to TextCtrl

Question

I have a TextCtrl and two events. One is bind the other is not

    self.rtb = wx.TextCtrl(self, ID_RTB, size=wx.Size(400,200),
                          style=wx.TE_MULTILINE | wx.TE_RICH2)

    wx.EVT_KEY_UP(self.rtb, self.OnRtbKeyUp)
    self.rtb.Bind(wx.EVT_TEXT_PASTE, self.OnPaste)

What is the difference? It seems that both events works fine.

I've read about Binding all sources explain how to use. None explains the difference between event that isn't bind to event that is bind.