Many people read about Google's advanced search operators on various SEO forums, but don't have a clear understanding of what they are, or how they are useful. Some of these operators include site, related, allintitle, allinurl, and allintext. To read Google's official explanation of some of these operators, you can go to the Advanced Search Operators page. Not all of these operators are listed on that page, but you can get an idea of what the non-listed ones mean simply by understanding the listed ones.