Most cars have some sort of alarm and possibly even an immobiliser built in to them to prevent them from being stolen. This type of alarm and immobiliser is often referred to a Manufactures standard alarm and immobiliser. Above this level of security you have Category alarms that have added security features making them even harder to steal and therefore not as much risk.
If you have a car and find that your insurance is high (particularly if the car is going to be parked in an area with a high crime rate, then it may be worth investing in an upgraded security system. Check with your insurance company how much cheap it would be with different types of alarm / immobiliser systems to find out which is the best one for you.
Not only can it save you money on your insurance but it can give you that added peace of mind that you car is more secure than with a standard system.