PageRank measure's a web page's importance.Search engines like Google fixes a rank for each website based on the keywords in domain name, content,design of website,TLD,Domain age, number of visitors,loading capacity etc.The Internet's users go to a search engine before reaching a web site.When someone types a product into a search engine, and if our web site is listed at the top of these results,they may visit our site and chances are there that they may become our customer.So to attain a good pagerank will be the aim for all websites/blogs.PageRank ranges from 0 to 10.The more you rank in search engines the more beneficial for you.
Now,there are many techniques to improve the pagerank like good quality in the site/blog, regular updates,interlinking posts,Good website design & uptime,social media,affiliate marketing etc and SEO is one such technique.It uses various techniques like usage of suggested keywords,sitemap creation,submission to search engines etc.Through such legal process one can gain the desired web presence.
The factors that Google considers are keywords in URL, Title, Text, Domain age,Number of visitors etc.It keeps updating the factors for page ranking. The companies that provide SEO also should update accordingly.If we get services from such a concerned company then we can definitely make SEO to be effective.I have used the SEV(Search Engine Visibility) from XnYnZ.com
as they provide keyword and suggested topics,submit the site to over 100 search engines and also provide reports which eventually improved my website traffic.