system
Given the following post, respond as if you're commenting on Reddit:
human
Understanding Node.js

Hey guys,

I'm a junior developer trying to understand Node.js a little better. I use it every day at work with React (in that I use the 'npm run server' and 'npm run client' commands) but I feel like I don't understand it very well. I want to change that.

I've done my share of Googling, and what I've come to learn is that it's a runtime for JavaScript. So then I asked myself "Cool, so what's a runtime?". A runtime pretty much runs code - feed it some code and it will give you an output. My understanding is that browsers have their own builtin runtime, which is why you can still run Javascript without Node.

"So why use Node?" Because is allows you to run your Javascript without a browser, and in a server instead. This makes it possible (or at least makes it easier) for me to give my code to a cloud service provider so I can access my work in the cloud. 

What other advantages are brought by using Node?

My next question is, what are the interactions between my browsers runtime and Node?

I know that these are covered in many online resources, but I'm not able to find anything that explains it in a way that makes sense to me. If anyone has any resources that explain the power of Node in a simple way it would be much appreciated. I just feel like I'm overthinking this, which is causing a mental block in my head.
gpt
Your browser runtime (client) and your server should be considered their own little bubble/machines that are trying to talk to each other.  In fact, they don't even have to share the same technology (in the case, they both use JavaScript, but the server could totally use something else, like Python or Php, or even Java or C ++ if you really want to). 

They communicate through HTTP web requests, the standard text based communication. Further formats could be placed on top of HTTP, making the content HTML, JSON, XML or just unformatted plain text, or binary data. 

Modern web framework will tend to help you with this process to make it easier, more "magical".  But at the end of the day, you can just imagine two people stranded on two islands, communicating to each other through mails in a bottle (requests). Whether the other party understand the message, or even got the message at all, or care to do anything about the mail in the bottle, or misunderstand the message and did something else instead. What they do on their own island is their own business. 

It is your job as a developer to keep them in line.  Now imagine one of them is not under your control, it will be really frustrating to understand what the other person is trying to say at all. That's why API is needed, that the other party that you don't control will promise to react to those bottles in a predictable way.