Preventive maintenance is just that – maintaining your vehicle on a regular basis to prevent more costly repairs down the road. The simplest example of preventive maintenance is an oil and filter change, so you're already familiar with the importance of keeping up with this regular maintenance item. Another example is your braking system. Having your brake system checked on a regular basis and even have certain wearable items such as brake pads and shoes replaced before they wear out will save you money in the long run.
While today's vehicles are build better and last longer, they do require some additional maintenance in order to keep them running properly, even though many of today's computers used on these vehicles can compensate or 'mask' certain minor problems for a while.