Imagine you're watching TV and you see someone who always seems to be showing you the coolest new videos, showing off the newest fashion, or interviewing your favorite celebrities - that person is called a VJ, or video jockey.
A VJ is a person who works in media, usually on TV or the internet, and is responsible for sharing videos or other content with you, the viewer. The VJ's job is to make sure they pick the best videos possible, and then share them with you in an entertaining or informative way.
Sometimes the VJ will also talk to you about the video, or give you some background information about the artist or subject. They might show you some cool dance moves or help you vote on your favorite videos, and they always try to make sure you're having a good time while watching.
Overall, a VJ is like a cool friend who knows all the best music and videos, and wants to share them with you in a fun and engaging way.