Can I ask a dumb question?

What is "triggering"?

Is it just feeling a strong negative emotion? Or something that is just a step away from suicidal/self-harming stuff?

I have to be honest. I've never been on a board where everything seems to be a "trigger". I'm actually wincing as a type this in anticipation that someone will say that this post is "triggering". My mother once went on a bizarre diet where every other food had to be avoided because it was a "trigger" food. She never explained what those foods "triggered" or how she even knew they were "triggering". All I knew was it made being around her difficult.

I can't imagine internet conversations ever triggering me to do anything. But sometimes fairly innocuous questions from people IRL can remind me about where I am in life, setting the table for self-pitying and depression. Is that what people mean by "trigger"?