Okay kiddo, long long ago in history, there was a group of people called the Tatars who lived in Central Asia. Now these Tatars were known for being very fierce and strong warriors, and they liked to travel around and conquer new lands.
So one day, the Tatars decided to start invading other countries. They would ride on their horses and attack villages and cities, taking whatever they wanted and sometimes even capturing people and making them their slaves.
These invasions were really scary for the people who lived in the places the Tatars attacked. They had to find ways to defend themselves, like building big walls around their cities or training soldiers to fight back.
Eventually, the Tatars made it all the way to Europe and started invading countries there too. They were able to conquer and rule over many places for a while, but eventually other powerful groups like the Mongols came along and defeated them.
So, in short, the Tatars were a group of warriors who liked to invade other countries and take over their lands. They were really good at fighting and caused a lot of trouble for the people they attacked.