Not really. Basically, you have a roster of a QB, 3 wide receivers, 2 running backs, a kicker, team defense, a utility player and a certain number of bench spots. You draft players from any NFL team to fill those spots. That is your 'team'.
Each week two teams in your fantasy league go head-to-head. Based on what the players of each team do stat wise, you earn points (ie. 6 points if your QB throws a touchdown, 6 points if your running back scores a touchdown, etc.) Whoever has the most points wins that week.