The timing belt in your vehicle keeps everything moving together and in sync, like the chain on a bicycle. It keeps everything moving as it should, but it also powers certain things inside the vehicle too.
The long and short of it is that it is a vital part of the car, and sometimes, it needs to be replaced.
As for when it needs to be replaced, it will be different for every car and your owners manual will have the answer, but it is typically between 60,000-100,000 miles in the car. The timing belt is made of rubber and so, over time, it will wear down, and it can actually break, which can land you in a sticky situation, and it can be extremely unsafe.
It is best to replace it before it breaks, so that nothing else is impacted during the damage process. You can get in touch to enquire more about this, as often there is no warning that your timing belt is on the way out.