I think that you want to know SERP and webpage rank...if yes..then SERP means that your site position in search engine and page rank is google determine site worth and rate that site out of 10..but there are lot of algorithms involved in Pare Rank as well as SERP
Page rank in SERPs is the rank you get by doing SEO on the particular keyword you opt for.And PAge rank of toolbar reflects the authority of your site,the more high the PR of your site the more it is seen as trust worthy.
1.Page rank Google’s page rank, also known as link juice is the culmination of backlinks to a site. Over time the amount of page rank you have, grows, or subsequently falls due to various reasons. The higher your pagerank is the more pages google will crawl on your site and the increased frequency in which they will visit your site. The actual number of your page rank is only known by google, inside the googleplex. 2.Toolbar page rank This is the page rank displayed on your google toolbar. It is generally update by google once every 4 months. However we have not had a full update now for 6+ months and counting. Its value is vague and often irrelevant. It varies from datacenter to datacenter and is never in “real†time. A page could have a PR 6 score but show TBPR of only 2 because it has not been updated in months.