METI or Messaging Extra-Terrestrial Intelligence is a way of sending messages to aliens in space. It's like sending a letter to someone, but instead of sending it to your friend who lives across the street, you're sending it to an alien who might live millions of miles away in outer space.
Scientists use special equipment, like big antennas, to send these messages. They send messages in different languages and use symbols and pictures that even aliens who don't speak our language might be able to understand.
But, scientists have to be careful when sending these messages because they don't want to accidentally send anything dangerous that might harm the aliens or Earth. So, they think very carefully about the information they send and the potential consequences.
Scientists are still debating whether sending these messages is a good idea. Some think it's important to reach out and communicate with other beings in the universe, while others worry that it could lead to harm or danger for us.
Overall, METI is like sending a message in a bottle out into the vast, unknown ocean of space, hoping that someday it will be found and understood by someone out there.