Hey kiddo, do you know that a long, long time ago, there was a powerful civilization called the Romans? Well, they conquered a lot of lands, and one of them was called Dacia.
Okay, imagine that you and I have two pieces of land, and I want to take over your land, and you don't want me to. That's how the Romans and the Dacians felt. The leader of the Romans was Emperor Trajan, and he wanted to control the Dacian land. So, he sent his army to fight against the Dacians.
After several wars and battles, the Romans finally won and took over Dacia. They renamed it Roman Dacia and made it a Roman province.
Now, what does it mean to be a Roman province, you ask? Well, it means that the Romans were in charge of the land, and they governed it. They built many things in Roman Dacia, like roads and bridges. They also brought their culture and way of life to the Dacians.
The Romans ruled over Dacia for a very long time, about 165 years. But eventually, they left, and the land became part of other kingdoms. However, the Romans left a big mark on the Dacian land, and even today, we can still see evidence of their existence in things like ruins and artifacts.
So, in short, Roman Dacia used to be a land called Dacia, but the Romans took it over and renamed it. They governed it and left a long-lasting impact on the land.