Synthetic engine oils are produced through a synthesis process that takes very small molecules and assembles them into larger designer molecules with premium lubricating properties. This is a personal choice, but we recommend using them.
You will need to look in your manual that came with your vehicle. If you did not get a manual (bought a used car), then there are plenty of places online to look up the proper maintenance for your vehicle. Please take it seriously! Most cars use synthetic oils and lubricants nowadays. They can usually go every 6 to 7 thousand miles between oil changes. But, once again...check with your manufacturer.
There are many ways to keep track of when you need to do what. Some people build a spreadsheet, while others simply download a simple scheduler that someone else made on the internet. Whatever you decide to do, please take it seriously! Your vehicle will last much longer with less breakdowns!