A search engine is a tool used to find data based on a particular input. Web search engines are one example where you can enter a word or phrase to find web pages that match those terms. Not every web search engine works the same way. Most of them are crawler based. It means that they actively seek the web for pages to add to their index. The search engine is what you use to quickly lookup information from the index and display the results on the page. Search engines are the primary method for browsing the web and there are many different kinds that are built for finding specific information. Within each search engine are often advanced search options that are used to focus your search better and help you find what you're looking for. Search engines automatically create website listings by using software often called spiders or spiderbots. These spiderbots crawl web pages. They follow a link of site to other pages and index the information in the process. The crawler bots behind the search engine scour the web not only by jumping from one link to the next but also by checking each site for a robots text file. This file contains a listing of which pages on the site a search engine should crawl. This is one way website owners can block a search engine from indexing a particular page. Software spiders return to pages that have already been crawled on a pretty regular basis to check for updates and changes. Everything they find goes back into the search engine database. Every search engine is different. But the common idea with all of them is to type something into a search box and wait for the results. Some search engines also have a reverse search option that lets you browse the web with something other than text. They can search a sound clip or picture file. Many search engines include extra features beyond just a simple search box. They let you interact with the index using special text commands or buttons that can filter the results and remove items that are not relevant to what you are looking for. Lots of search engines exist and the one you choose to use should depend on what you want to do with it. Web page search engine are often multi purposed. They locate all sorts of data from general web pages and news to help documents. Image search engines search for photos and drawings. Video search engines find all kinds of videos and live streams. People search engines locate people on the internet using their name and address. A regular search engine that's optimized for searching and displaying results on a smaller screen are called mobile search engines. Job search engines are designed to find job postings. Invisible web search engines are the tools that browse the invisible web. There is no need to manually update a search engine so that you are getting the most updated results in your searches. If you are seeing really old results that you suspect should be updated. But actually you might just need to clear the cache of browser. Search engines do not search the entire web. There are portions of the web that are not crawlable by a search engine.