Action handlers are just JavaScript functions with a particular function signature.
Action handlers are also known as –
1. controller action
2. controller function
Declaring an Action Handler –
For example you have Action Handler named handleClick
handleClick: function(component, event, helper)
3 parameters that are part of this Action Handler are –
1. component – The component which called this Action Handler.
2. event – The event which caused this Action Handler to be called.
3. helper – the component’s helper, another JavaScript resource of reusable functions.