How the Search Engine Works ?

Search engine is the popular term for an information retrieval (IR) system. While researchers and developers take a broader view of IR systems, consumers think of them more in terms of what they want the systems to do — namely search the Web, or an intranet, or a database. Actually consumers would really prefer a finding engine, rather than a search engine.
Search engines match queries against an index that they create. The index consists of the words in each document, plus pointers to their locations within the documents. This is called an inverted file. A search engine or IR system comprises four essential modules:

• A document processor
• A query processor
• A search and matching function
• A ranking capability

While users focus on "search," the search and matching function is only one of the four modules. Each of these four modules may cause the expected or unexpected results that consumers get when they use a search engine.