and my understanding is: a leader lead a group of people to achieve the common goals; whereas a manager accomplish the task,assigned by the leader, through people effors.
Leader leads a team with group cohesion. he/she doesn't have to have authority to control his/her group members, however, he/ she could maximize everyone's potential to benefit the group; drive the intrinsic motivation of his/her group members; make his/her group to accompolish shared objectives by supporting each other. Manager has the authority to take charge of evey group member. There may or may not have cooperation within his or her group. my point