...
"Offset" in which position the control circle is located (0 means the begin of the spline and 1 end of the spline).
"Vortex" adds a clockwise (positive values) or counter clockwise (negative values) twist to the particles. The particles might leave their path with high settings, but you will also get a more turbulent fluid.
"AxisAxial" attracts (positive values) particles towards the spline or repels (negative values) them. This way it is possible to create a thinner or thicker particle stream.
"Radial" moves the particles from one control circle to another. Particles outside the circles will not be attracted and leave the path.
"Radius" The circle scope is adjusted with "Radius" or the gizmo handles.
...