Rain in Delhi-NCR due to ‘influence of low-pressure area, monsoon trough’: What does that mean?

<iframe
  src="https://hindustansphere.com/embed/cluster/70c82373333bf1784097502e5519e476b9844732"
  width="100%" height="320"
  style="border:0;max-width:680px"
  loading="lazy"
  title="Rain in Delhi-NCR due to ‘influence of low-pressure area, monsoon trough’: What does that mean?"></iframe>