It's used for downloading files (and occasionally uploading them) over HTTP(S). It has plenty of other features but that's what it's used for 99% of the time.
What do you think it is used for?
What do you think it is used for?
Also smart phones, smart watches and TVs generally don't use libcurl for that. Android, iOS and WebOS have their own HTTP stacks. I don't know about cars or consoles.
Nearly every videogame for instance use libcurl as their HTTP stack. You know why? Because it's the best HTTP library for C/C++.
If you have a C/C++ application doing HTTP traffic it's likely using cURL. Or, I dunno, you could look at this page to find out: https://curl.se/docs/companies.html