It taught itself to play chess in a few hours hours and then went onto to beat the top computational chess computer. Here is the key sentence.
The computer it beat is a dumb machine crunching ridiculous amounts of data to decide which is the most advantageous move. The AI computer is able to focus on calculations that will win the game relying on what it already knows about previous games.Indeed, much like humans, AlphaZero searches fewer positions that its predecessors. The paper claims that it looks at "only" 80,000 positions per second, compared to Stockfish's 70 million per second.
This is why AI tech is so important going forward. It's simply not possible to teach a computer everything nor is it possible to provide them with the resources to utilize that data. e.g. a car cannot drive itself if it requires a computer the size of refrigerator, at least not in any practical sense. As the AI tech improves the resources they require get smaller, not bigger.