Free/Libre/Open-Source Software is widely available, and you probably use some of it without even knowing.
Free Software grants you four freedoms; the freedom to run the program as you wish, the freedom to make copies and share the software, the freedom to study the source code and make changes if you know how; and the freedom to share your modified versions of the software.
There is a large variety of Free Software; and most of it is available free of cost.
--Popular Free Software you may have heard of.--
Firefox
Chromium (what Chrome browser is based off of)
Audacity (audio editing)
Ardour (Music composition)
Minetest (A wonderful and superior Minecraft clone(100% free of cost to play))
Blender (Full featured and powerful 3D modeling/Animation Software)
Godot (Free/Libre game engine. Design anything from a complex 3D game, to a simple sidescroller)
Krita (Painting application)
GNU Image Manipulation Program (GIMP) (Not as powerful as Photoshop, but still quite powerful and feature-ful)
Inkscape (another graphics drawing program)
Strawberry Music Player
OBS Studio (Stream to a plethora of live streaming websites like Twitch)
VLC Media Player (You've probably used it; but, you may not have known it's Libre Software)
Libre Office (A full featured office suite)
Only Office (Another full featured office suite)
And literally tens of thousands of other programs.
Most people will recognize the term, 'open source software', so you can use that in a search engine to find software. Free Software activists prefer the term Free Software however, as we believe proprietary software poses an existential threat to human rights and liberty.
You can also head on over to
https://alternativeto.net/, and use it to search for Free/Libre/Open-Source software alternatives to popular proprietary software programs.
Linux Mint is a good beginner Operating System, for anyone interested in ditching Windows and giving
GNU/Linux a try. There are literally
100's of other GNU/Linux based operating systems to choose from, many of them are quite user friendly these days.