In the story of a burning house, a father promises his children various toy carts as a ruse to get them to come out of the burning house.
So the children leave the house. But once they have come out of the house, the father just gives them all one large cart to play with.
This story is meant to signify how the Buddha, like the father, uses whatever means are necessary to convey the truth of the Dharma to people, even if they are very ignorant.