Google is ramping up their productivity suite by bringing add-on extensions to Google Docs and Sheets. This means users will now be able to browse different extensions for Docs and Sheets that can do things like add a built-in bibliography to a paper, or create labels within a document, all through several third-party add-ons. These add-ons are synced through your Google account, so they’re carried across all of your documents automatically.
Currently, there’s just a handful of add-ons available, but Google expects that to increase pretty quickly. Among the first few available are Avery, an extension for making and printing labels, EasyBib, an easy way to create a bibliography for your paper, and Merge, which allows users to send customized emails from Docs. They’re pretty useful and you can start playing with them right away.
source: Google Drive Blog