Ember action syntax differences

I've read the documentation about the actions hash, but in every example I can find, people leave off the action: when observers are used.

like this one:

http://ift.tt/197C1aB

They favor the action name direction under the extend definition just like how properties are defined, and an anonymous function is defined wtihin that property.

My question is what are the differences between these two ways?

Does it not bubble up if you don't use actions:?

If you don't use actions:, does it not bubble up to routes?

And most importantly, what does this mean for using observers?

http://ift.tt/1CuAib5