Okay kiddo, have you ever played hide and seek with your friends? Imagine that you are playing hide and seek with your friend, but instead of hiding behind a tree or under a table, you are hiding a secret message inside another message. This is called a subliminal channel.
A subliminal channel is a way to hide a message inside another message without anyone noticing it. It is like a secret language that only a few people know how to read. Just like when you write a letter to your friend, you can write a secret message inside the letter that no one else can read. This way, only your friend will know what the secret message is.
In the same way, subliminal channels hide secret messages inside messages that other people can see. For example, a website that wants to secretly send a message to its employees could use a subliminal channel to do it. They might hide a message in the pictures or sounds on the website that only their employees will notice.
But don't worry, subliminal channels are usually used for harmless things like sending secret messages. They are not used to harm anyone or make people do things they don't want to do. So, now you know what a subliminal channel is, just like when you play hide and seek with your friends.