I'm not a car person....can someone help?

The knocking you hear is called detonation. This is not good for your engine. It is caused by low octane but also because your engines timing is set very high. The lower the timing the less knock you will hear but also the less power and performance you will have. So to counter act the knocking you could either back off on the timing just a little, or you could switch to a higher grade of gasoline. Octane boost additives will quiet the knocking as well but should be viewed as a contaminant. Also you should check your air filter. It is dirty and in need of replacing I bet. Hope this helps