Most search engines and databases search "words anywhere" or "keywords" automatically unless you select another type of search.
Keyword searching finds matches for your terms in any field of a record or any part of a Web page, so you will typically retrieve more information with less precision. This is known as "recall" searching because it focuses on recalling as much information as possible.
Databases and search engines may allow searching in specific fields such as author, title, url (Web address), or subject and will sometimes refer to this as "advanced," or "expert" searching. These searches will typically retrieve less information with more precision. This is called "precision" searching because it focuses on finding only precisely what you need.For example
If you are a detective & the only clues you have for a missing persons case are the words "red," "blue," and "green," in the picture below, each of the five people on the left is wearing red, green and blue. Any of them could be a match. This is keyword searching.
RED + BLUE + GREEN
If instead you knew your person had a red tie, blue shirt, and a green beret, you have a better chance of finding the right person. This is field searching.
Tie=RED, Shirt=BLUE, Beret=GREEN
Only one person in the picture on the right matches these criteria.