Most likely Yahoo.
Wallow, the main concept behind fantasy football is how well your team performs against the team of another Manager (you, me, Titus, etc). At the beginning of the league, there will be a draft where you pick certain individual players to form your team. So you want to draft a QB, RBs, WRs, so on and so forth. Basically you want to get the best guys available at every position to make your team.
Once your team is assembled, each week your team faces another Manager's team. Each player on your team's score will be added up to form your overall score for the week. If your overall score is better than the team you're facing, you win. If it's not, you lose for the week.
This goes on for 17 weeks. It's pretty fun.
If you have any questions, let me know.
WE STILL NEED MORE PEOPLE!