Ember app trigger action in component

In my Ember app component my-component.hbs, I have

Now in my-component.js, I have it defined as action below;

actions: {
    gridInstantiated: function (myGrid) {       
    }
}

How/Why does the above syntax for action work ? Specifically

1. "gridInstantiated" is not defined as normal property in my-component.js
2. In the hbs, it is defined without the "action" keyword

Just wanted to know how it works given the above 2 points ?