AC adapter, batteries and laptops

Do AC adapters for laptops work just like PSUs in a typical desktop? Is there any other power generation in a laptop besides this and the battery? What is the efficiency of the AC adapter to computer components, AC adapter to battery, and battery to computer components?

laptop adaptors usually put out between 15 and 19v iirc so I presume that then gets converted into 12, 5 and 3.3 after entering the laptop.

I have an AC adapter for my laptop rated for 65W at 19.5V with Efficiency Level IV (I can't seem to find more on this)