Aqua regia (königswasser in German) is a very corrosive liquid made from a mixture of nitric acid and hydrochloric acid (1:2 - 1:3). This chemical mixture is so corrosive that it can even dissolve gold, and that's what you'll learn about in this video.
The aqua regia will need to be heated to advance the chemical reaction, due to the low concentration of nitric acid. Highly toxic nitrous oxides will begin to form in the aqua regia, and soon the mixture will turn into tetrachloroauric(III) acid (aurochloric acid). This gold compound can be used in further chemical experiments, and to form different gold compounds.