Ember Sending actions from component

I was going through the official Ember guide for sending actions from component;

http://ift.tt/1NsJ5vs

However it sounds quite confusing to me. Basically I have the following questions;

1. What is the best way to handle sending of actions from a custom component ? Differences in triggering/handling actions from component template V/s normal template ?
2. What does sendAction() do exactly ? How can we pass parameters from our component ?
3. Any example where we can understand the reusability difference clearly ?