Kyrios is a word that comes from ancient Greece and it means "lord" or "master". Imagine that you have a big sister or a big brother who is much older than you and knows more about the world. You might call them "kyrios" because they are the boss and they have more power than you do.
In ancient times, people used the word kyrios to show respect to people who were more important or powerful than they were, like kings or rulers. They might call these people "kyrios" to show that they recognized their authority.
Kyrios is also a word that can be used in religion to talk about God or Jesus. Christians sometimes use the word kyrios to show that they believe that God is the boss and has power over everything in the world.
So, basically, kyrios is a fancy word that means "boss" or "master" and it's used to show respect to people who have more authority or power, or to refer to God as the ultimate boss.