It seems possible (as I learned from a comment to this question made by user55822) to use a command in order to search a term on the web by using "keybinding" the way Aretha is used.

What the aforementioned user says is that

"you could search mouse selection anywhere by using an app like Artha, or by keybinding sh -c 'firefox "http://translate.google.com/#en/fr/$(xclip -o)"' (example given translate english into french)"

A lot of things are obscure for me here. I could use Artha or keybinding (as alternative), or both? How to do that in each case?

and

"The command I gave you will open google translate in Firefox with your mouse selection (text highlighted) as a query. Use sh -c 'firefox "https://www.google.com/search?q=$(xclip -o)"' if you want regular Google over Google translate. And obviously, that would work everywhere"

I do not know what to do with that formula. What should I do exactly? How to use it? In what application?