Hey Topo - isn't there an American "football" team in Barcelona, maybe called the Dragons?
Anyway, what happens in a fantasy league is that, there is a real professional league that has teams in cities all across the US. Owners of fantasy league teams will "draft" players from these teams. The real teams play once a week usually, and how the players on your fantasy team do in their real games determines how your fantasy team does. Depending on the fantasy league, there will be more detailed rules, but that's the general idea.
Personally I prefer the kind of football that Brazil won the WOrld Cup for recently (called soccer in the US).