Search Engine is a program that helps users find information about websites or any topic available on the World Wide Web.

Definition of a Search Engine:
A search engine is a software program that searches a database of internet resources (websites, web pages, images, videos, etc.) based on keywords or phrases provided by the user. It helps users quickly and efficiently locate the desired information on the internet.

Working of a Search Engine:
1. Crawling: Search engines use web crawlers or spiders to discover and scan websites. These crawlers follow links from one page to another, collecting information about the content and structure of each webpage they encounter.

2. Indexing: After crawling, search engines organize the collected data into an index. The index is like a massive catalog that contains information about the words and their location on different webpages. This process allows search engines to retrieve relevant results quickly.

3. Ranking: When a user enters a search query, the search engine retrieves relevant pages from the index. The search engine's algorithm then analyzes various factors, such as keyword relevance, page quality, and user experience, to determine the ranking of the search results. The most relevant and high-quality pages are displayed at the top of the search results page.

4. Displaying Results: After ranking the search results, the search engine displays them in a user-friendly format. Users can click on the search results to visit the respective websites and access the desired information.

Importance of a Search Engine:
- Saves Time: Search engines provide quick access to vast amounts of information, saving users time and effort in finding relevant content.
- Accessibility: Search engines make the internet accessible to users by providing an easy-to-use interface for searching and retrieving information.
- Discoverability: Search engines help users discover new websites, products, services, and resources by presenting relevant results based on their search queries.
- Research and Learning: Search engines are valuable tools for research and learning, as they facilitate the exploration of various topics and provide access to a wide range of educational resources.

In conclusion, a search engine is a crucial program that assists users in finding information on the internet. It plays a vital role in making the vast amount of online content accessible and discoverable to users worldwide.