Alexa is a California based subsidiary company of Amazon.com which is widely known for its website and toolbar. This Alexa toolbar congregates browsing behavior data and send it to website, where the data is analyzed and stored and create reports for company's web traffic. Also, Alexa provides data concerned with traffic, global ranking and other additional information for a website.
Alexa provides a numerical value to your website measuring the traffic flow and popularity of your website in search engines.
It's a traffic ranking. The lower the better. Your ranking means that you are ranked 772,242 for most traffic of websites on the internet. Only those with the Alexa toolbar send traffic data back, so it's not very accurate in most cases. An alexa under 100,000 is considered descent, but can easily be skewed by the demographics of your users. Websites with alot of experienced web users and webmasters are more likely to have the toolbar installed.
The algorithm according to which Alexa traffic ranking is calculated, is simple. It is based on the amount of traffic recorded from users that have the Alexa toolbar installed over a period of three months. This traffic is based on such parameters as reach and page views.
Alexa Rank is more of your visitors are getting alerted of the Alexa Ranking. When visitors came to your site for the first time and they saw your site ranked in millions, they would think that they're the only one visiting the site and very few else did. Alexa Ranking provides you an immediate view of you and your competitors' performance comparison.
Alexa Internet, Inc. is a California-based company that provides commercial web traffic data and analytics. It is a wholly owned subsidiary of Amazon.com. Founded as an independent company in 1996, Alexa was acquired by Amazon in 1999.
Alexa ranking is a ranking system that basically audits and makes public the frequency of visits to various sites. If you want to calculate the rating, I wish you to know that it is quite simple. It is based on the number of visits who had the Alexa toolbar installed for at least 3 months.