Donald Trump and Elon Musk: what's the deal?

Donald Trump has made his way to the White House, with a huge boost from Elon Musk. Of course, as expected and previously hinted at, Musk has also secured a new position as Trump announced that Elon Musk and former Republican presidential candidate Vivek Ramaswamy would lead the newly created Department of Government Efficiency. This duo is one of the most controversial ever. So what's the deal between these two and what impact will this relationship have on the world?