– This parameter the number of control points for each particle.

– The number of control points is important for the interactive editing.

– 10 segments should be sufficient even for very long hair, 5 segments for shorter hair, and 2 or 3 segments for short fur.

– In this example some hairs are rendered with a big radius, you can notice how 16 segments give the hairs a greater freedom of movement than 4 segments do.

Blender Hair Emission Segments