It's usually over-promoting a skill on your resume. It might not be nefarious or intentional, but it's a communications gap. What you mean by "experience in," and what the manager wants you to mean by "experience in," are two totally different things.
Example, if you read a SQL book a couple of years ago, you would say you have experience in SQL. You've forgotten most of it, but you are familiar. If a manager reads that same thing, he or she might think, "Oh, proficient in CRUD queries but not overly complex ones." Manager gives you a quiz on SQL, but since you don't have Google in front of you, you flail because you haven't messed with it in a long time.
It's not really lying, it's just a communications gap. I'm not saying there isn't outright misrepresentation of skills, but most of the time it isn't intentional.
With a truly technical manager, this is honestly one of the fastest ways to torpedo your credibility.
Anything listed on your resume is fair game for questions, especially if you claim it as a skill. "Reading a book" is not a skill; reading a book and using the contents in that book for several real world projects probably qualifies. Especially if you can describe what you did in detail.
Harsh reality: I value everything in that section of the resume at the value of the weakest component that I find. So when we discover that your knowledge of SQL is reading a few tutorials on w3schools ten years ago, I rate EVERYTHING ELSE in that section at the same level (ouch!).
So the safe way to play this is don't list anything that you can't hold a 5 - 10 minute conversation about and explain at least the basics of how the technology works, citing real examples of where you used it (paid or unpaid, I don't care about that, as long as you're clear about what you did).
Yeah. Most of your competitors won't do this. They'll fill out the bottom of their resume with junk. But um... there's a reason they're still looking....
Incidentally my own (technical) resume has exactly two lines of IT skills... each of which I can do a 30+ min speech on. Never had a problem in that area during an interview...
Example, if you read a SQL book a couple of years ago, you would say you have experience in SQL. You've forgotten most of it, but you are familiar. If a manager reads that same thing, he or she might think, "Oh, proficient in CRUD queries but not overly complex ones." Manager gives you a quiz on SQL, but since you don't have Google in front of you, you flail because you haven't messed with it in a long time.
It's not really lying, it's just a communications gap. I'm not saying there isn't outright misrepresentation of skills, but most of the time it isn't intentional.