super()

Super() is a call to the overriden method concerned in the super or parent class.

For the click event it does not serve any purpose since there is no change in functionallity if you remove it and you will not get any error.

For example:

if you create a class myCLASS1 and then inherit from it and override a method on it the call to super will execute the code from the inherited class.

If you remove super that code will not be executed and you may write different code for this method in the child class.

Simple :)