In the bottom toolbar on the far right next to the date and time. You will see this icon. This is the inking icon.
If you click on it you have the option to use a Whiteboard or do a Fullscreen Snip. Fullscreen Snips are great for webpages that you might want to mark-up, while the Whiteboard works just like a Whiteboard and pen. The three dots let you learn more about the inking options and change your pen options.
Your laptop will flip back into a tablet mode which makes these inking capabilities very helpful.