Visualisation is when you can visualise something in your head. If you don't know what visualise means or is, it's when you are picturing a scene in your head about anything.
What you should try to understand Visualisation.
Think about What you would see.
Think about What you would smell.
Think about What you would hear.
Think about all of those and visualise it in your head.It's really helpful for reading because when your reading a story or a chapter book or whatever else you may call them, you can easily picture everything in your head by visualising it.