Karaite Judaism is a type of Judaism where people believe that only the Hebrew Bible, also called the Tanakh, is the most important religious text. They don't believe in other religious texts or traditions that other Jewish people follow.
Think of it like a game of soccer. Imagine there are two teams playing, but one team only follows the rules that are written in the rule book, while the other team follows the rules in the book and also some other rules that their coach has made up. Karaite Judaism is like the team that only follows the rules in the book, while other Jewish people follow both the rules in the book and other traditions.
Karaite Jewish people pay attention to the way the Tanakh is written and try to understand it very carefully. They might have different ideas about how to celebrate holidays or what some of the rules in the book mean, but they all agree on one thing: that the Tanakh is the most important of all the religious texts.
So, in summary, Karaite Judaism is like a special type of Judaism where people only focus on one important religious text, which is the Hebrew Bible, and don't follow other traditions or religious texts that other Jewish people do.