Search engine: definition and function

How does a search engine work?

Most search engines work in four central steps:

• Crawling: search engines use special programmes called spiders, bots or crawlers to search the internet. They do this on a regular basis and look at pages again and again. The crawlers pick up new or outdated content in the process. This content is then indexed and evaluated.
• Indexing: The data collected by the crawlers is analysed, organised and stored in an index. There, the search engine can quickly find suitable information for all possible search queries. Like the index at the end of a book, but much more detailed, this search engine archive contains an entry for every word on every indexed website. In addition to the textual comparisons, other filters also apply.
• Search: When a user submits a query to a search engine, the latter must translate the words used into terms that relate to its index. Today, this is done using a variety of advanced technologies, including natural language processing (NLP). Machine learning is playing an increasingly important role here. The result of the translation process is a listing that identifies the important parts of the search query, corrects spelling errors where necessary and adds synonyms. The search engine then consults its index to find websites that "match" the optimised query.
• Ranking: Finally, search engines use algorithms to present a list of matching results. The SERPs contain what the respective search service considers to be the best answers to the search query - ranked by relevance. For very vague questions, today's search engines can provide helpful interpretations. These include definitions of terms, translations, suggestions for photos or videos, contextual extensions of search terms and more.