How Search Engines Work
Now that you’ve learned what SEO is, the next step is understanding how search engine’s work. Crawling, indexing content and mapping results are the main tasks of search engines, through which they rank sites for users based on the search parameters.
Small programs such as crawlers, bots or spiders investigate and index web pages on the Internet regularly to find out new or updated content, and this process is called crawling.
These so-called spiders visit each website to detect the links of every page and add them to a list. All new sites, any changes tp existing sites and any broken links are updated in the search engine index. Though this process is done for free, some search engines serve a paid submission service with guaranteed crawling. Usually they guarantee inclusion in the index, but they do not help with search ranking.
Indexing starts after collecting and organizing all the pages that a spider finds. By this process, search engines examine the key HTML code elements such as page title, “meta” tags and “alt” attributes to determine the content type.
When there is a search query, search engines begin to match the most relevant elements from the index and deliver the search results. Different search terms will return different results. At first it returns the results that are relevant to query and then ranks those results in order of perceived usefulness. Currently 200 factors are used to determin the relevancy and these continue to be adjusted. The search engine ranking appears lower or higher depends on the keywords and phrases being used.