I had to start with Googling, to know what Android WebView is. So, here it is:
A View that displays web pages. This class is the basis upon which you can roll your own web browser or simply display some online content within your Activity. It uses the WebKit rendering engine to display web pages and includes methods to navigate forward and backward through a history, zoom in and out, perform text searches and more.
So, it is what Android apps use (or can use) to display web content. Now, to the news.
The Android 4.4, KitKat release contains a new WebView implementation built on Chromium open source technology.
More details here.