For extra context, I asked this question earlier, and thought I understood things, but not anymore.

I know that echo ignores stdin. I know that stdin, stderr and stdout exist and, in this context, I don't know that "things" other than these exist.

So, if echo ignores stdin, where does it get its input from? It seems like stdin, stdout and stderr do not tell the whole story.

I'm sorry I can't ask a more objective question, I feel like I don't have enough understanding to formulate what I want to ask.

For extra context, I asked this question earlier, and thought I understood things, but not anymore.

I know that echo ignores stdin. I know that stdin, stderr and stdout exist and, in this context, I don't know that "things" other than these exist.

So, if echo ignores stdin, where does it get its input from? It seems like stdin, stdout and stderr do not tell the whole story.