I don't know about Ensight, but generally speaking, streamlines are:

"(...) a family of curves that are instantaneously tangent to the velocity vector of the flow. These show the direction in which a massless fluid element will travel at any point in time"

whereas pathlines are

"the trajectories that individual fluid particles follow. These can be thought of as "recording" the path of a fluid element in the flow over a certain period. The direction the path takes will be determined by the streamlines of the fluid at each moment in time."

Quoted from the link below.

Streamlines characterise velocity vector field. Wheras the pathline is an actual tarjectory of a particle.

I suppose in some cases streamlines an pathlines do coincide, like when velocity field is constant and the particles travel with the flow, without experiencing external forces like gravity or buoyancy.

https://en.wikipedia.org/wiki/Streamlines,_streaklines,_and_pathlines

@Anton Ishmurzin thank you so much for your reply. It helped me understanding pathlines and streamlines in Ensight as well. It is the same concept.

Thanks again.

Pathlines and streamlines do coincide if the motion of the fluid is stationary i.e.when the partial derivative of the velocity with respect to  time (not the total  or lagrangian derivative) is zero.