How does insider trading work?

I’m not even sure if the examples I’m talking about are called “insider trading”, I just don’t really know what to call it other than that. Because insider trading has to do with stocks or something right?

I’m talking about say you work for a bio company or something, and you know, they have their confidential procedures, experiments and equipment. Say a disgruntled worker wants to expose those secrets for money. How do they even do that? I mean, is there like a forum where they can be like, “Hi, I’m Bill and I’m selling a super secret death ray” ?

When I went to college a while ago, someone was working in the library archives, and he apparently was selling historical documents to “other people.” I was surprised because how could a 20-something year old in college even contact whoever wants to buy them? In short – how the hell do people sell confidential information/materials?