In laymans terms FIFA is the body that runs world football. Sepp Blatter is the president and he gets elected every 4 years or so. For a long time now everyone has assumed that the organisation was corrupt based on some of the decisions it was taking, like awarding the 2018 World Cup to Russia despite its human rights violations and invasion of the Crimea and the 2022 version to Qatar despite the fact that it would mean players playing in 50 deg+ temps.
Blatter keeps getting re elected because he has the block support of places like Africa, Asia and the Caribbean. This is because he sends millions and millions of $ each year to them to help them improve the game in their countries but, and here's the key bit, he doesn't ask them to justify what they spent the money on. So these countries do a lot of 'fact finding' missions on large expense accounts and build lavish headquarters for themselves. As to the corruption Blatter must be up to his neck in it or terribly thick IMHO.