Apps Script is versatile. Among other things, you can:
- Add custom menus, dialogs, and sidebars to Google Docs, Sheets, and Forms.
- Write custom functions for Google Sheets.
- Publish web apps — either standalone or embedded in Google Sites.
- Interact with other Google services, including AdSense, Analytics, Calendar, Drive, Gmail, and Maps.
- Build add-ons to extend Google Docs, Sheets, Slides, and Forms, and publish them to the Add-on store.