Gatekeeping in communication is like being a doorman, but for information. You know how the doorman only allows certain people into a fancy hotel or club? Well, gatekeepers are like that too, but they decide what information gets to be shared and who gets to share it.
For example, when you want to tell your mom about something, but your little brother doesn't want you to, he may try to be the gatekeeper and stop you from telling her. Or, in the news, reporters and editors are the gatekeepers who decide what stories to cover and how to present them.
Sometimes gatekeepers can be good because they make sure the information is accurate and helpful. Other times, gatekeepers can be bad if they only allow certain people to talk or if they leave out important information. It's important to have a mix of voices and opinions in communication and gatekeeping can affect that.