A typical automobile will have the following fluid compartments, which need to be checked and fluid levels maintained:
Water/coolant -low water level in your radiator could result in severe engine damage from overheating
Power steering fluid - low levels can burn out the bearings in the power steering pump and cause steering to lock.
Oil - the most common cause of premature engine wear, causing the pistons to seize inside the engine.
Transmission fluid - low fluid levels can cause the transmission to "slip" or shift into the wrong gear, burning out the transmission and resulting in engine damage.
Brake fluid - Improper levels can prevent the brakes from engaging properly, which may result in severe, or fatal accidents.
Each of these fluids perform a vital function and can cause a dangerous vehicle malfunction if neglected. Looking under the hood may seem overwhelming, but the fluid compartments are well marked. The recommendations are in the Owner's Manual and often printed right on the fluid compartment. Keeping close tabs on the fluids will make your vehicle safer and add years to its life.