To answer your question, first of all, the window.location.href is not a method but rather is a property that will tell you the current location of the URL of the browser. Following which, by changing the value of the property which will redirect the page.
The window.open() is a method that you can pass a URL to that you want to open in a new window.
window.location.href = 'http://www.google.com'; //Will take you to Google.
window.open('http://www.google.com'); //This will open Google in a new window.
Please note that window.open() can be passed through additional parameters.