What is the difference between project manager and project leader ?

There is only one project leader, but a large project may have several project managers, each managing a particular aspect of the project.

In a small project, there may be only one project manager who is of course also the project leader.

A project leader is a project manager, but a project manager is not necessarily a project leader. 

Both managers and leaders are professionals who are tasked with planning, executing and closing a project. Both are in charge of a project team, but only project leaders inspire and motivate the team. Project leaders take the time to get to know the team, keep them in the loop and act as mentors.