Okay kiddo, imagine you're playing a game with your friends and you're the boss of the game. You get to make all the rules and tell your friends what to do. That's sort of like what a Roman Dictator was.
In ancient Rome, they had a special person called a dictator. But instead of playing a game, they were in charge of the entire country when something really bad happened. For example, if the country was at war and the regular leaders (called consuls) were not able to solve the problem, they would call on a dictator to come and fix things.
The dictator would have almost all the power in Rome and could make any decision they wanted to solve the problem. They would be like the boss of the country, telling everyone what to do and making sure they did it. But don't worry, kiddo, they were only in charge for a short time, usually about six months.
The important thing about a Roman Dictator was that they were appointed, not elected. That means someone else picked them to be the boss, instead of the people voting for them, and once the problem was fixed, they would give up all their power and go back to being a regular person again.
So, a Roman Dictator was like a temporary boss who helped fix big problems in ancient Rome. They were appointed (not elected) and had almost all the power in the country for a short time. But remember, they didn't stay in charge forever and went back to being a regular person after their job was done.