I am trying to interpret the results of HYSPLIT back trajectory run for the following input parameters

Location : Chennai, India

Trajectory: Back Trajectory

Duration: 96 hours

Height: 10 meters

Meteorological file used: NCAR Reanalysis file

I have downloaded the 2017 year file and have run the back trajectory analysis for the said location for 96 hours. I have used OpenAir software to plot path. My questions are as follows:

1) Does the trajectory indicates the motion of particles backward to the source from various locations?

2)How do we explain the methodology of motion of the particles? Can anyone provide me with a source?

I have attached the file to perhaps make it easy to understand what I am asking.