It is usually assumed that if you are discussing something on Lambda the Ultimate, that you already understand the jargon and by using it, you are using a language that everybody (the target audience - in this case, language lawyers and language enthusiasts, I guess) understands and is well defined.
Sure, they could use terms that are easier to understand to the uninitiated, but then you risk having to explain your terms every time because people use different ways to refer to the same thing. Jargon evolves precisely to solve that problem, at the cost of making it harder for somebody new to understand.
Obviously when learning these things, you need a clear and easy to understand description of the terms, but as others have stated, a book usually does this, while blogs and research papers probably assume you already know whats what.