Very First, PR refers to Page Rank, which is a Web tools service from Google, considering different categories of a website like contents, articles, blogs quality as well as free from copy, paste, spam, white hat SEO, etc. And PR starts with “0” to “10”.
Alexa Internet Inc, is a California based subsidiary of Amazon.com. Alexa rank consisted with a listing of all websites on the web which are sorted by traffic. Basically Alexa gives rank to websites calculating the website’s last three months traffic, total page views and user reach. Alexa rank starts with infinity and comes down to 1.