attributes vs properties

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  //hello: 'city',
  init() {   
    this._super(...arguments);
    console.log('init');
    this.set('hello', 'city');
     console.log('init ',this.attrs, ' Hello ',this.get('hello'));
  },
  didReceiveAttrs(){
    console.log('didReceiveAttrs ',this.attrs, ' Hello ',this.get('hello'));
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
{{input value=name}}
<br>
{{my-component hello='world' name=name}}
<br>
{{outlet}}
<br>
<br>

templates.components.my-component.hbs

{{hello}}
{{yield}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}