Lecture Notes: How Google Search Works

Introduction

• Billions of users search Google daily.
• Questions about Google’s own functioning often arise.
• Aim: Provide a concise explanation of Google Search.

Google’s Web Mapping and Indexing

• Google continuously maps the web, creating an index of hundreds of billions of pages.
• This index acts like a library, used when searching for terms like "lasagna."

Understanding Search Queries

• Ranking Algorithms:
  • Purpose: Understand user intent, even with incorrect spelling or vague terms.
  • Function: Sifts through the index for relevant information, prioritizing it for the user.

Factors Influencing Search Rankings

• Keywords:
  • Presence of search terms on pages is crucial.
  • Location of keywords (titles, captions) is also significant.
• Links:
  • Links between pages help determine importance and trustworthiness.
• Location:
  • Geographical location affects search results (e.g., local events).
• Recency:
  • Recent updates on pages are more likely to have current information.

Spam and Scam Detection

• Many sites are not legitimate and attempt to scam users.
• Google’s algorithms aim to preemptively flag these sites to keep them out of search results.

Google’s Continuous Updates

• Change Adaptation:
  • The web and search queries are constantly evolving.
  • Google updates search thousands of times per year.
• Search Quality Raters:
  • Human raters evaluate changes by comparing search results.
  • Feedback helps ensure updates enhance search quality.
  • Raters follow published guidelines on what constitutes a good search result.
  • Note: Rater feedback influences evaluation but doesn’t directly alter ranking.

Conclusion

• Google analyzes and organizes web content to provide reliable and useful information quickly.
• Further resources available for in-depth understanding:
  • Google’s dedicated "How Search Works" website.
  • Search Quality Rater Guidelines available for public access.