i have been confusing whether the game is inside the world or world is inside the game.?
Hello @nagFlapjacks, as far as i remember, world is just a group object inside game itself.
If you check this repo which is phaser-ce, and inside here under core/Game.js, there you can see this first:
/**
* @property {Phaser.World} world - Reference to the world.
*/
this.world = null;
After this when you check the boot method of this Game, you can see this line
this.world = new Phaser.World(this);
And so far you can always check the source code when you can’t figure something out 
Another thing that you can also check what is this Phaser.World is, where you will see:
Phaser.World = function (game)
{
Phaser.Group.call(this, game, null, '__world', false);
...
When we create the Phaser.World it has just a reference to the game itself
hello @hcakar, thanks for that, one small query do we add physics, camera, etc stuff to the world or game.?
Hey @nagFlapjacks, same thing again you could check the source code but here it is: