Howdy,
what were those things called Venn diagrams? the two circles thingy. It's like take two circles, each representing TEACHER and LEADER respectively and overlap them. Some persons are teachers but not necessarily leaders, ala the old adage "those who can't do, teach", whereas Leadership seems to imply by definition action and activity beyond just oral instruction.
So following the overlapping circles there are some leaders which are not teachers but because they are inspirational, brave, or simply take the lead in the activity or seek to cause others to follow their example, they are leaders.
then you have the ones that are both.
but you asked for differences and my point is that one can't really speak of differences in general since each case would be situational. There might be no real difference between a teacher and a leader, they could and perhaps are often the same.
In another perspective you could have a big circle representing LEADER and a smaller circle within the Leader circle which represents TEACHER because in a sense every teacher is a leader in that they "lead" their pupil(s) either in the learning or obtainment of knowledge or in some other instruction whereas not every Leader is a teacher.
But again to speak of differences doesn't really seem to make sense without some concrete example or unless you are comparing two or more different persons
-Eduardo