Cassius makes great points about FOSS (Free and Open Source Software). I'll add few more points to encourage people to give it a go:
-) FOSS gives its users freedom of usage, adjustment and modification that is absent from close source software
-) It's easy to combine different pieces of software to get required results, i.e. get output from program A and give it as input to program B for further processing. It may sound unimpressive and quite alien to people who haven't been exposed to Linux but I promise it opens gateway of limitless possibilities.
-) FOSS does what it was designed to do instead of pretending to do something when in actuality its main purpose is to collect user data, send it to a producer who sells it to the highest bidder.
And here's a list of the software I use most often. A lot of these programs are terminal based but I prefer them to GUI programs because of their extensibility and speed.
Arch Linux - operating system
i3 - windows manager
Neovim - text editor, both for general purpose writing and light coding, combined with Groff software for document formatting
sc-im - spreadsheet editor
Firefox - web browser
Newsboat - RSS reader
MPV - media player
CMUS - music player
Sxiv - image viewer
Zathura - document viewer
Xournalpp - pdf editor
nnn - file browser
Syncthing - synchronization