Free software scares normal people

If handbrake scares them, don’t you dare to demonstrate how to use ffmpeg. I remember when I used handbrake for the first time and thought “wow, it’s much more convenient than struggling with ffmpeg”.

If you only care about converting media without tweaking anything, ffmpeg offers the simplest UI ever.

    ffmpeg -i input.avi output.mp4

Proposing a CLI command as a candidate for "simplest UI ever" is a great gag.

Come on. "type ffmpeg, then hyphen i then the input filename then the output filename". I would've understood this when I was 8. Because I was super smart? No, because I was making a genuine effort.

The portion you've overlooked is there is an entire population of users out there who have never seen, nor used, a command line, and telling them to "just type this out" ignores all the background command line knowledge necessary to successfully "just type this out":

1) They have to know how to get to a command line somewhere/how (most of this group of users would be stymied right here and get no further along);

2) They now have to change the current directory of their CLI that they did get open to the location in their filesystem where the video is actually stored (for the tiny sliver who get past #1 above, this will stymie most of them, as they have no idea exactly where on disk their "Downloads" [or other meta-directory item] is actually located);

3) For the very few who actually get to this step, unless they already have ffmpeg installed on their PATH, they will get a command not found error after typing the command, ending their progress unless they now go and install ffmpeg;

4) For the very very few who would make it here, almost all of them will now have to accurately type out every character in "a-really_big_filename with spaces .mov", as they will not know anything about filename completion to let the shell do this for them. And if the filename does have spaces, and many will, they now need to somehow know 4a) that they have to escape the spaces and 4b) how to go about escaping the spaces, or they will instead get some ffmpeg error (hopefully just 'file not found', but with the extra parameters that unescaped spaces will create, it might just be a variant of "unknown option switch" error instead).

This describes me somewhat. I use FEA software and only recently started using it to execute jobs in CLI. I still trip over changing directories. Fortunately notepad++ has an option to open CLI with the filepath of the currently open file. I also didn't know right-click is paste in CLI. Don't use ctrl+c accidentally. But ctrl+v does work in powershell (sometimes?). "Error, command not found" is puzzling to me. Where does the software need to live relative to the directory I am using? This is all still very foreign to me, and working in CLI feels like flipping light switches in a dark room.

To answer your last question, on your operating system there is something called “PATH”. It is a user- or systemwide variable that dictates where to look for programs. It basically is a list of directories, often separated by “:” Further reading: https://www.java.com/en/download/help/path.html (this may have Java references but still applies)