Possession in soccer is the ability to move the ball around the pitch in efforts to unbalance the opponent and advance the ball. However, possession is more than just keeping the ball away from the opponent by kicking the ball around the field. Possession is about movement, vision, teamwork, chemistry, creativity, and can often keep your team from fatiguing before their opponent.
Where possession alone will not win the game, past seasons of the Premier League's winning teams are among the top possession percentage holders. Possession alone will significantly increase your chances of winning games and is a much more sexy style of soccer.