Greeting is when you say hello to someone when you meet them. Just like when you see your friend or teacher, you might say "hello" or "hi". It's a way of showing that you are happy to see them and it's a nice thing to do. Different people greet in different ways, like with a wave or a smile, and some cultures have their own special greetings, like "namaste" in India or bowing in Japan. Remember, it's always polite to greet someone when you see them!