  A new feature of the rotating black holes is the existence in their
ergosphere of trajectories of particles with negative and zero energies. Here
we analyze general properties of such trajectories comparing them with usual
trajectories of particles with positive energy. A comparison with the situation
in rotating coordinate frame in Minkowski space-time is made. The possibility
of the unbounded growth of the energy of two colliding particles in the centre
of mass frame in the ergosphere is analysed.
