Looking to save money because Microsoft Office is sooooo expensive? LibreOffice is the way to go. It works on Windows, Mac and Linux. It also both opens and saves Microsoft Office documents including Word, Excel and PowerPoint. Its not perfect. Don't try and open up those very complicated documents with embedded forms or with custom programming behind the documents. For 99% of the docs that you'll find in your office, LibreOffice will do the trick.
Libre Office is built around the ODF standardized file format but can also fully open files from Microsoft Word, Excel, Powerpoint and even PDFs. Its completely free to use and is open source.
Like Microsoft Office, it includes a Spreadsheet program, presentation program and writing program but with the different names of Calc, Impress, and Writer.
All about LibreOffice Alternative to Microsoft Office
The official website for this software utility can be found at: https://www.libreoffice.org/download/libreoffice-still/