Have you recently discovered a puddle underneath your car after it was parked for a while? If so, your car is likely leaking a liquid, and you should be concerned about getting this problem repaired. However, the actual liquid will tell you what kind of problem you have and how urgent it is to get repaired. 

Antifreeze

The purpose of antifreeze is to regulate the temperature of your vehicle's engine. If you see it on the ground, the liquid is usually sticky, while being green or yellow in color. While it is not good to see antifreeze leaking out of your car, this is not a fluid leak that requires you to drop everything you are doing and visit a mechanic. Take your car in for auto repair at your earliest convenience to have the leak looked at

Brake Fluid

Brake fluid is a much bigger concern to see underneath your vehicle, since it is the fluid that helps your brakes function properly. The fluid itself is going to be oily and light brown in color. If you see brake fluid, take your car in to get repaired immediately, since the safety of your vehicle is compromised by having a lack of brake fluid. 

Motor Oil

Does your vehicle have a persistent motor oil leak, causing you to occasionally put more oil into the vehicle to keep the levels to the proper level? This is not good, since that motor oil keeps all the parts within your engine well lubricated when they move. You'll notice motor oil because it looks like a thin syrup that is black or light brown in color. You should be fine if you wait a while to get this problem fixed, since a slow leak will be fine as long as you monitor the motor oil levels. But have a mechanic investigate why the oil is leaking in the first place. 

Power Steering Fluid

Power steering fluid is unique in color, since it is the only one that can have a red color to it. If it's dirty, it will look more brown than red. The texture itself is thin, and will drip from the front portion of the car where the engine is located. This fluid leak is a major concern, because it helps with steering the car on the road. Have it investigated immediately. 

Water

Your air conditioner will produce condensation that will leak onto the ground under your car. If the liquid is clear and thin, you have nothing to worry about. Save yourself a trip to the auto shop due to this harmless liquid leaking from your vehicle.