Plus Symbol (+)
When you searched apple by itself, you should have gotten results relating to Apple, the technology company. By adding +fruit you were able to see results relating to the fruit apple.
Minus Symbol (-)
When you searched restaurants near me, you should have gotten all kinds of results about restaurants in your area. By adding -breakfast, you were able to see restaurants without breakfast.
Quotation Marks (" ")
When you searched free cookie recipes, there should have been tons of results that had at least one of those words in them. By adding quotation marks around the keywords, you were able to find results that had those keywords in the exact order you typed them.
When you searched cheetah, all kinds of results showed up, and most of them were unreliable. By searching within National Geographic, you were able to find accurate information about cheetahs.
By searching mitosis, you got loads of pages relating to mitosis. By adding filetype:ppt you were able to find powerpoint presentations about mitosis.