The charcoal will absorb the grill lighter fluid and when lit, the fluid burns not only at the surface, but also from the inside of the charcoal. For this reason the charcoal will be ready for use much quicker.
However, please be aware that this is a liquid and DO NOT pore the liquid directly on a hot grill or glowing charcoal to speed up the ignition process. Never use the liquid when children are present when igniting your grill. If you have children at the grill the better and safer choice would be to use the firelighter cubes.