Don't worry about it. Keep working and learning and focus on doing great work that makes people happy. As long as you take the time to learn why something works, rather than just cutting-and-pasting from StackOverflow, you'll be fine.

Frankly, the recommendations @seibelj is making are in a particular niche--OS fundamentals--and one that I'm guessing makes him feel smart knowing about. But they aren't necessarily relevant to you, or important to know. It depends on what you work on. Some people have trouble realizing that their pet interview question isn't actually as universal as they think it is.

PS: IPC is "Interprocess communication," and it's how you can have multiple processes coordinate with each other. You may have heard of pipes or sockets--those are for IPC. (Technically, so are files.) If not, don't worry about it. I have over 20 years' experience as a professional developer and while IPC primitives like pipes and sockets have come up from time to time, it's hardly central to my work.