A digital twin is just that a copy of something from the physical world made digital with as much detail as possible. A digital twin is useful for project planning, spatial  awareness, product development and high detailed mapping. Need to order a new larger generator in an exiting room but don't know if it will fit? Digital twin can help without before ever ordering a single thing. Need to know how a building will look on the side of a hill? That's a good use for a digital twin as well. Need to estimate the cost of remodeling a run down building but can only visit the sight once?  Perfect use for a digital twin. Wanna see the big picture of your yearly projects to a property years in advance? That too is a great use of a digital twin. Wanna interact in virtual reality with your product before spending money on manufacturing? Guess what?  You'll need a digital twin.