What distinguishes a first line manager from a team leader?

Question

How do companies determine that employees would be good managers?

Answer 1

First line manager: mainly focuses of day to day activites, team leader is one who is taking a group to do the not so routine.
http://managementhelp.org/mgmnt/defntion.htm

Second question: There are many answers to this, often contradictory. In my experience, dealing with change in a positive way (ie, embracing change) is a sign of a potential manager. People skills are important, as well as raw intelligence.