Google Sheets is a spreadsheet program included as part of the free, web-based Google Docs Editors suite offered by Google. The service also includes: Google Docs, Google Slides, Google Drawings, Google Forms, Google Sites and Google Keep.
Google Sheets is free, and it's bundled with Google Drive, Docs, and Slides to share files, documents, and presentations online. It includes almost all of the same spreadsheet functions—if you know how to use Excel, you'll feel at home in Google Sheets.