3D 'printing' has been around at least 20 years. In the early 1990s I had injection moulding prototypes made that way. It was done by solidifying a transparent liquid resin.
But something has changed to make the machines cheap. They used to cost thousands. The prototypes were also very pricey - a few hundred quid, presumably to recover the cost of the machine.
Structurally they were flimsy, and were used to prove the product fitted together dimensionally. Or you could rub them down to get a smooth finish and paint them, for
PR shoot etc purposes.
Sintering metals in 3D is really clever.