There are Mazda 3 Timing Belts and Timing Chains in this list.
There are serious issues with a bad timing belt or timing chain.It can lead to permanent engine damage if it jumps a tooth.This doesn't happen to your Mazda 3 if you know the symptoms of a bad timing belt.
Unlike a timing chain which looks a lot like a bicycle chain, timing belts are made out of rubber and nylon.There is more on a timing chain.They create the same symptoms when they go bad.
Timing belts are not very common.Cars and trucks are more likely to have a timing chain than belts.Japanese made cars can use timing belts instead of a timing chain.Four cylinder engines are where they are found most.
The timing can go wrong.The Mazda 3's timing belt or chain needs to be kept in the right amount of pressure.As the belt stretches through normal operation, it would fall off or jump.Keeping a consistent amount of force on the belt is what the tensioner does.As the belt stretches it adjusts.The timing belt will fail if the tensioner is not keeping enough pressure.