If you need a full writing suite (e.g., docs, spreadsheets, presentations, etc) and want something other than Google Docs/etc, check out LibreOffice. https://www.libreoffice.org/
ETA: Open Office, which is mentioned below, is another office suite. It goes back and forth which is better between Open and Libre. I’ve heard that lately Libre is being maintained and updated more frequently, but honestly, look at both and check for yourself. 