Search for Adam Smith = 38,700,000 results
Search for "Adam Smith" = 2,730,000 results
Search for theory of relativity = 3,430,000 results
Search for "theory of relativity" = 856,000 results
Combining search terms with AND will:
Search for politics = 296 million results
Search for "college student" AND politics = 43 million results more focused on your topic
Search for "college student" AND politics AND "2008 election" = 543,000 more relevant results
Often, these features are easiest to use (or only available in) the Advanced Search option. (example)
Most search tools have ways to limit the results list and the options are often on the left side of the results page. Limiters usually include date ranges, topics, languages, authors, and formats.
You can also add additional terms to your search to narrow down the results.