GNU Prolog is a program that helps computers understand how to solve problems using a type of language called Prolog.
Prolog is like a game where you ask the computer questions, and it gives you an answer based on a set of rules. For example, if you ask the computer "Is it raining?" and the rules say "If it's cloudy and the humidity is high, then it's probably raining," then the computer will tell you yes or no based on the current weather conditions.
GNU Prolog helps you write these sets of rules and helps the computer use them to arrive at an answer. It can be used for things like artificial intelligence, databases, and decision making.
So, in short, GNU Prolog is a program that helps computers understand how to solve problems using a special language called Prolog.