Why is the World Cup the best sporting competition?
The World Cup is a global event that happens only once every four years. It always has a Host(s) Nation, which is the only team that automatically qualifies for the tournament. Various tournaments lead up to the event, leading to the qualification for the World Cup. From there, FIFA will rank the qualifiers in different tiers and draw them via lottery into "Groups" together. 

The Qualification process is available to all teams across the globe. Regionally-based tournaments hosted by the likes of CONACAF, UEFA, CAF, CONMEBOl, etc lead up to the World Cup Tournament. 

Once the Groups are drawn via lottery together, all Four teams (from different regions). They play against each other and the two teams with the highest total points will advance to the elimination rounds, which include a round of 16, Quarterfinals, Semifinals, and the Final. Once the elimination round begins they are single elimination matches the loser is out of the tournament and the winner advances to the next round.