Your aircon will often leave a puddle of water under the car after driving. As long as this is only from your aircon then this is normal and not something to worry about.
How does that work?
Warm air from the car is cooled and this creates water vapor (condensation). The water droplets are discharged via the air conditioning system to the drip tray and then discharged outside through a hose. A puddle is formed. Don't be alarmed, there's nothing wrong!
If the puddle under the car is coloured, pay attention. This could indicate leaking coolant or oil.