010101 I guess when you do a yarn command in your tutorials you are doing something a little different.
It has the same effect.
npm is the original package manager for Node.js that was born about 10 years ago. The company maintains the npmjs.com website, the npm public registry and the
npm terminal utility that is usually bundled with Node.js.
The npm history is quite bumpy, and there was a period where very little improvements were made to the
npm CLI. One of the main problems was that it was veeery slow to install packages (still faster than
composer though). It also had some other annoying bugs and weird behaviours.
So some alternatives were born, the most popular being
yarn by Facebook.
yarn still uses the npm public registry (it actually mirrors it on Facebook's servers) but provides a different terminal utility that does similar things, presumably better. It was a common opinion that it was true (and a fact wrt performance), at the time, but today
npm is much better than it was and has catched up on many aspects, so as far as I'm concerned there aren't many reasons to prefer
npm today. I found
npm to be actually faster than
yarn in my limited testing.
In short, I would suggest to stick with
npm unless you have a real reason for not using it. There's a lot more documentation and resources about npm than yarn on the web.