What this basically means is the lower the resistance of your coil the more power you are able to pump through it, which in turn produces more heat leading to faster vapor production with thicker denser vape clouds.
Sound a little technical, don't worry, let me explain.
Your battery releases a charge to your coil (Amps) and generally the lower resistance of your coil the more power you can push through it. The more power you can push through your coil the faster it heats.
The faster your coil heats, the faster it can vaporize your e liquid resulting in a thicker, denser vapor cloud.