Introduction

Internet connectivity is ruling the globe in current scenario, and it is virtually unfeasible to find anything on the web without utilizing a search engine. But the question is what this search engine is? A search engine is complex software which may be compared to be a finder visiting to the various websites and their pages which help the searcher to find significant data (Levene, 2010). Search engine optimization (SEO) can be defined as a mechanism which allows the searcher to get most appropriate results of his online search. SEO also helps marketers by displaying their respective ads to the right people in the right place and right time. Marketers can advance the rankings of their advertisement on the search-results pages by improving their quality score in order make them more significant and therefore more searchengine compatible (Sen, 2005). Search engines can be classified into three sorts: • Crawler-based search engines: Crawler or Spider programs create databases by methods for web robots. These robots are programs that dwell on a host system and recover data from destinations on the web utilizing standard conventions. Basically, they naturally venture to every part of the Web taking after connections from records and gathering data as indicated by the HTML structure of the record (Thelwall, 2015). • Human-powered directories: Human-powered directories additionally alluded as “open index system” relies upon human-based exercises for postings. Site proprietor presents a short portrayal of the site to the registry alongside category it is to be recorded. Submitted site is then physically looked into and included the suitable class or rejected for posting. Keywords entered in the search box will be coordinated with the portrayal of the locales. A decent site with great substance will probably be assessed for nothing contrasted with a site with poor substance (Burghardt, Heckner, & Wolff, 2012). • Hybrid search tools: Hybrid search engines utilize both crawler-based and manual ordering for postings the locales in list results. A large portion of the crawler-based web indexes like Google fundamentally utilizes crawlers as an essential component and manual screening as an auxiliary instrument. At the point when a site is being distinguished for spam exercises, manual survey is required before incorporating it again in the query items (Ahlers, 2012). Attributable to the massive amount of data on the Web, ideal from the beginning of the Web, web crawlers have turned into an irreplaceable instrument for web clients. The underlying foundations of search engine innovation are in data recovery systems, which can be followed back to the work at IBM amid the late 1950s. Data recovery has been a dynamic field inside data science from then and has been given a major lift since the 1990s with the new prerequisites that the Internet had brought (Oppenheim, Morris, McKnight, & Lowley, 2000). One of the issues related with the assessment of web search tools is the reality that they are always showing signs of change, and building up their search instruments and user interface. Also, consistently observes the innovation of new web search tools. Joining these truths with the always showing signs of change substance of the web, it is clear that no particular assessment of an Internet search engines is probably going to stay legitimate for any period of time. Subsequently, most researchers stress that the results of the search engines are just demonstrative of the execution of those web crawlers around at that time only (Kammerer & Gerjets, 2012).