Lactose Free Milk is real milk.
But the difference between Lactose Free Milk and regular milk is that the Lactose Free Milk has an added enzyme called Lactase that breaks down the natural Sugar in the milk which is called Lactose so that the lactose free milk becomes lactose free.
The Lactase enzyme added to the milk and other dairy products as well make it so that people who are Lactose Intolerant can still enjoy and consume those dairy products.
I'm Lactose Intolerant myself and have been since a kid and I love milk so I'm glad that there's Lactose Free Milk available.
I always have to have my morning cereal and milk so the Lactose free milk makes it possible to still have my cereal and milk.