The plant will produce energy by concentrating solar power onto pipes containing water. The water will boil, and be used to spin turbines. Once shipped off-shore, the islands could be used to convert seawater to hydrogen, allowing them to be autonomous and untethered to the shore. The hydrogen could be picked up by barges, instead of having to transport the electricity to shore via a physical connection. Link
This pilot project is being designed mostly to test the feasibility of the solar islands; CSEM says that the islands so far look like they will be cost-effective as long as they are deployed in areas with more than 350 days of sunlight that are near the equator. That's a lot of sunlight, but the area of the coast of the UAE fits the bill. Of course, it's also necessary for the structures to be able to survive a serious storm either by motoring to shore to avoid it, or being resilient enough to live through it.