The FIDE world cup features the best players in the world. There will be 6 rounds where each player plays eachother twice. If there is a tie, a tiebreak will be played to determine the winner. The top finishers in this event will go on to play in the 2020 World candidates tournament - the winner of this event gets to challenge Magnus Carlsen for the 2020 World Championship.
Chess 24 is one of my favorite sources for news in the chess world, and I will recommend articles from www.chess24.com from time to time: https://chess24.com/en/read/news/the-2019-khanty-mansiysk-world-cup-begins