Google OS is built off of Google Chrome. Google Chrome is therefore much different from Internet Explorer and Mozilla Firefox such that everything is built in to Google Chrome so there is no need to install extra software to open or use other software. For example, Google Chrome has Adobe Flash built in to it whereas Internet Explorer does not. This explains why Google Chrome can play Adobe Flash based content within the Google Chrome browser. It also has Adobe Reader builtin, explaining why you can open up a PDF within the Google Chrome browser.