AI-Completeness is a concept from Artificial Intelligence (AI). It describes a type of problem that is so difficult for a computer to solve that it almost seems impossible. AI-complete problems require a lot of computing power and often take a long time to solve. In some cases, they may never be solved. An example of an AI-complete problem is the game of chess. It's very difficult for a computer to not only make good moves but also be able to predict what the opponent will do next. AI-Completeness is a difficult concept to understand and it's impossible to explain it to a 5 year old, so it's probably best to just say that AI-Completeness is like a really tough puzzle that computers find difficult to solve.