Theory:

LibreOffice is an effective and free office suite, a successor to OpenOffice (.org), used by millions of people worldwide. Its clean interface and feature-rich tools help to unleash the user's creativity and enhance their productivity.
 
The LibreOffice suite consists of programs such as word processing, creating and editing of spreadsheets, slideshows, diagrams and drawings, working with databases, and composing mathematical formulae that make it the most versatile Free and Open Source office suite on the market:
  • Writer (word processing)
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  • Calc (spreadsheets)
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  • Impress (presentations)
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  • Draw (vector graphics and flowcharts)
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  • Base (databases)
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  • Math (formula editing)
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LibreOffice is compatible with a broad range of document formats such as Microsoft Word (.doc, .docx), Microsoft Excel (.xls, .xlsx), Microsoft PowerPoint (.ppt, .pptx) and Publisher.
 
But LibreOffice works with its native support for a modern and open standard, the Open Document Format (ODF). With LibreOffice, you have maximum control over your data and content – and you can export your work in many different formats, including PDF.
 
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Fig. - LibreOffice Homepage
 
LibreOffice is Free and Open Source Software, possible for everyone to use, share and modify, and created by a worldwide society of hundreds of developers. This software is tested and used daily by a large number of users.
Reference:
https://www.libreoffice.org/discover/
https://en.wikipedia.org/wiki/LibreOffice_Writer
https://commons.wikimedia.org/wiki/File:LibreOffice_6.1_Calc_Icon.svg
https://commons.wikimedia.org/wiki/File:LibreOffice_6.1_Impress_Icon.svg
https://commons.wikimedia.org/wiki/File:LibreOffice_Draw_icon_3.3.1_48_px.svg
https://commons.wikimedia.org/wiki/File:LibreOffice_6.1_Base_Icon.svg
https://commons.wikimedia.org/wiki/File:LibreOffice_6.1_Math_Icon.svg
https://upload.wikimedia.org/wikipedia/commons/4/42/Libreoffice_6.2_initial_screen_screenshot.png