A web search engine is a specialized software system designed to retrieve information from the vast expanse of the World Wide Web. Web searching is facilitated through the use of search engines, which operate in a sequential manner:
User Query:
The search process begins when a user enters a query into the search engine. This query could be a few words or a more complex expression of information needs.
Web Crawling:
- Web crawling is the initial stage in which search engines deploy robots, commonly known as crawlers or spiders, to discover new and updated content on the web. This content can take various forms, including webpages, images, videos, PDFs, etc.
Indexing:
- Indexing involves the incorporation of information about a webpage into the search engine's index. The index serves as a database, encompassing information about the pages explored by search engine spiders. The index organizes and catalogs detailed data about the content and topical relevance of each webpage. It also includes a map of all the pages linked to by each page, the clickable (anchor) text of links, and additional information about the links (such as whether they are advertisements, their location on the page, and other contextual aspects). This index acts as the repository from which search engines retrieve and store data when a user enters a query into the search engine.
Ranking:
- Ranking is a critical step where the search engine evaluates the relevance of indexed pages to the user's query. Various algorithms are used to assign a ranking score to each page based on factors like keyword relevance, page authority, and user experience. Pages with higher scores are presented at the top of the search results.
Retrieval and Presentation:
- When a user initiates a search, the search engine retrieves relevant pages from the index based on the ranking scores. The results are then presented to the user in a structured manner, typically as a list of links along with brief descriptions.