Matka is a very popular game in Mumbai and in Gujarat. It originated as a game called Ankadar Jugar, when people would bet on the closing price of cotton in the New York stock exchange.
Classic Matka is a little different to the Mumbai game. There are two draws of three numbers per hour, these are called the opening draw and the closing draw. They are drawn at half past and on the hour. They are drawn from a pack of cards with numbers zero to nine. So a typical draw might be 469. The numbers of the draw are added up, so it would be 19 in this case. The last number is taken and so the opening number would be 9 (as you just take the second number) so the draw would be represented like this: 469 9X. The next draw is the closing draw, it might be 257, which would make the closing number 4 (from the 14) and the full draw would be displayed as 469 9X4 257.
People bet on all of these outcomes at various odds. People bet on the two three digit numbers. They bet on the opening and closing numbers (In this case 9 and 4). They also bet on the opening and closing number combined (In this case 94). Finally they bet on the sums of the opening and closing draws (In this case 19 and 14).