能帮解释一下这段代码！

Private Sub Command1_Click()
Text1.Text = UCase(Text1.Tag) '.tag属性是存控件额外属性，ucase将某字符串转成全部大写
End Sub

Private Sub Command2_Click()
Text1.Text = LCase(Text1.Tag) '转小写
End Sub

Private Sub Command3_Click()
Text1.Text = Text1.Tag '将text1.tag赋值给text1.text，此时text1控件内容就为tag属性里存的数据
End Sub

Private Sub Text1_KeyUp(KeyCode As Integer, Shift As Integer)
Text1.Tag = Text1.Text '在text1键盘弹起事件里 文本内容赋值给.tag这个属性
End Sub