Koine Greek is a language that was spoken a long, long time ago in parts of the world like Greece and Israel. It was a special type of Greek that people spoke during a time called the Hellenistic period, around 300 BC to 300 AD.
Now, speaking Koine Greek was kind of like having a secret code language that only a few people knew how to use. It was important because it made it easier for people from different places to communicate with one another. So, just like how we speak different languages today, back then, people had their own special languages too. However, Koine Greek was like a common language that people from different areas would use to understand each other.
It's important to know that Koine Greek was different from the fancy type of Greek that people spoke before it, which was called Classical Greek. While classical Greek was used for things like literature, philosophy, and drama, Koine Greek was more of a "normal" person's language, used by regular folks in everyday life.
So, if you were living during the time when Koine Greek was spoken, you would speak it to talk to people who lived far away from you or if you wanted to learn something new from someone with a different background than yours. It was a very special language that helped people to connect with each other in ways that they couldn't have done otherwise!