According to Wikipedia, American football (referred to as football in the USA and also known as gridiron) is a sport played by two teams of eleven players on a rectangular field with goalposts at each end. The offense, the team with control of the oval-shaped football, attempts to ...bla bla bla...ZZZ
You're already lost don't worry, David Robinson, will make it crystal clear and also explain the cultural impact in the U.S. society.
David onws a Miami-based law office that helps people who wants to settle in Florida and he's a big fan of US football. So you'll have the luck to understand at last the rules and to ask him questions over a glass of wine after the presentation.