Released alongside the iPad Pro, the Apple Pencil let's you draw, take notes, mark up documents, annotate photos and do basically anything you can do with a traditional pencil.
You still have to charge it via the Lightning connector, which you can do by sticking it directly into your iPad's Lightning port.
Powering all this is a tiny 3.
One big difference is that the Apple Pencil 2 charges magnetically while attached to newer iPads, meaning there is no Lightning connector at the end that you use.