Google Calendar is an get a button on its browser toolbar that they can easily click to see upcoming events from google calendar, without ever leaving their page. And if they are on sites that have special events encoded, it can click the button to instantly add events to they calendar.
Hypertext Markup Language (HTML) is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScript.
Typekit is an online service which offers a subscription library of high-quality fonts. The fonts may be used directly on websites or synced via Adobe Creative Cloud to applications on the subscriber's computers.