You can assign various roles for your players in the team. Player roles can be accessed by clicking on the Assign Player Roles button in the Tactics page. If multiple players are assigned the same role, the player at the top of the list will take precedence over the ones below him.
This is the captain of your team who takes on pitch decisions. Captains require good Leadership qualities to be able to lead the team efficiently.
Normally all freekicks that your team are awarded wil be taken by them. But other players may also take freekicks if it is in a defensive position or near your own goal.
All corner kicks are taken by these players. Corner kicks usually are aerial passes, so it is wise to not assign your players with the best Heading attributes to take corner kicks.
Freekicks and corners require good Passing ability to successfully deliver the ball. The goalkeeper never takes freekicks regardless of whether you assign him the role or not.
They take your spot kick whether they be penalties awarded during the game, or during a penalty shootout tie-breaker. Use players with good Shooting to get the ball past the opposition goalkeeper.