If when you turn the key to the "Start" position, you hear the starter cranking as usually, but the car doesn't start, then the problem is most likely not with the starting system.
If when you turn the ignition key to the "Start" position and nothing happens, or all you hear is just a click, or the starter cranks very slow then you probably have a problem with one of the component of the starting system. Most often, it's the battery or the starter motor itself.
The alternator is one of the hardest working electrical components in your vehicle. When your vehicle is running the alternator is busy creating electricity to provide the engine and the car accessories with needed power.
A battery is needed to power the operating system of your car. Once the vehicle is running an alternator that is driven by the engine charges the battery. While in operation the alternator creates electricity, about 13.6 to 14.3 volts, and recharges the battery to its original state of charge.
When the car is not running and your battery charge IS LOW, some electrical components such as alarms, ARE operatING. if the system voltage is low, it can cause erratic symptoms
YOUR CAR has many fuses, some protect very little like a rear windshield wiper while others protect major system circuits, like the engine management system.
A fuse is designed to break stopping the voltage flow in the event of a power overload or short circuit. Each vehicle has several fuses that are necessary to safe guard electrical circuits. An electrical circuit will always fail at the point of highest resistance. Most of the time that point is the fuse holder.