What does each component of 'get input motion state' represent?

I was once reading an article on how the browsers provide rotation info of mobile devices and I thought maybe UE provides the info in a similar way. Using that API you can actually get the rotation values around each “axis” of the device and then use it in your application. To make it clear here is the link to that article.

https://dev.opera.com/articles/w3c-device-orientation-usage/