Timer induces the washing machine to perform washing in the exact specified length of time. The start switch in the machine is generally a part of the timer knob and helps in the setting of the time for the proper cycle of washing to take place. Pulling or pushing the knob makes it to activate accordingly. There are two types called the digital and mechanical types. It can be installed only with the help and advice of the professional repair person.
The above list is not exhaustive, but it's a great starting point. Washing machine repair is by no means a simple task, but it becomes a lot more manageable for the average homeowner when you're at least somewhat familiar with the parts that you're looking at. Take a minute to look over the owner's manual that you received when you purchased your current unit; there should be a complete diagram with all of the parts labeled. If you misplaced the manual or can't locate a helpful diagram, there are countless online resources that can help you with your DIY repair by allowing you to look up your exact model specifications and helping you identify exactly which parts may be at the root of your washer's malfunction.