Google Apps Script is free to use, and all you need to get started is a Google account.
You can do a lot of things, like automatically transfer your emails from Gmail to Drive based on your labeling, give deadlines to tasks and sync it with Google Calendar to get notifications. In a lot of ways, you can use Google Apps Script like an ‘if-this-then-that’ condition to get things done.

Google spreadsheet

• Automate spreadsheet
• Using 3rd party API in a spreadsheet-like Xero, MailChimp, Cryptocurrency, etc..
• Custom menus in sheets
• Custom buttons in sheets associated with the script
• Data Processing
• Send an email automatically
• Triggers
• Copy or cut data within or between sheets/docs with scripts or manually Assist in the editing of sheets/docs

Gmail, Drive

• Automation related to Gmail, G Drive
• Email Parsing, mail Forwarding, auto Mailing, etc…
• Accessing, deleting, creating files and folders in the drive

Google docs, Slides

• Adding/modifying data from or sheet to doc, slides or vice versa
• Changing styles, layouts, etc.
• Custom menus in docs
• Any other thing in docs/slides

Calendar

• Creating events in calendars using data in sheets
• Updating existing events
• Sending invites to the guests
• Any other task in calendars

Forms

• Generating dynamic forms using sheets data
• Linking with sheets

INTEGRATION VIA REST APIs IN GOOGLE APPS SCRIPT:

• Airtable: Backup tables to Google Sheets; Create/delete rows automatically
• Hubspot: Retrieve contacts from lists
• MailChimp: Retrieve all existing subscribers
• Pipedrive: Get a list of activities
• Trello: Create new card; add attachments to an existing card
• Xero: Update invoice data in Google Sheets (send & receive)
• Quickbooks
• Lodgify
• woocomerce
• Google Maps API
• Many more…

Other Posts

• Basic of Google Apps Script
• What Google Apps Script can Do?
• How to set trigger in google apps script