Frank Cameron Jackson is a really smart man who studies things like philosophy and psychology. He's like a science detective who tries to figure out how our minds work and how we understand the world around us.
One thing that Frank Cameron Jackson is really well known for is something called the "knowledge argument." Basically, he asks us to imagine that there's a brilliant scientist named Mary who knows everything there is to know about the color red. She's read every book and studied every experiment about red, but she's never actually seen it herself.
One day, Mary gets to look at a red apple for the very first time. Even though she knew everything there was to know about red, seeing it in real life is a completely different experience.
Frank Cameron Jackson uses this example to argue that there are some things about the world that we can only understand by experiencing them firsthand. No matter how much we read or study, there are some things we just can't fully "know" until we see or feel them for ourselves.