Page Rank - It’s a Google’s way of deciding the importance of a webpage. Page Rank is a numeric value given by Google to the webpage which defines how important the page is on web. Google calculate the page rank of a webpage by taking its entire inbound links and on-page factors into account. Page rank matters because it is one of the factors that determine a page's ranking in the search results.

Pay Per Click (PPC) - An advertising program in which textual ads are listed on a search engine. It can also be defined as a ad promotion technique used on websites, advertising networks, and search engines. The advertisers bid on that “keyword” which they believe as a sales keyword. Potential visitors looking for that particular product type that keyword in the search bar, see their ad, and click on it to buy. So, the point here is the advertisers or webmasters should be more specific about the keyword which is related to the sales of their products and services. The webmasters pay only if an end user(visitor) clicks on the ad.

Pay for Inclusion (PFI) -For few years in the past, many of the search engines (except Google) have introduced a simple PFI model so you could speed up the indexing of any page of your site by paying a fee. So, PFI is nothing but the fee charged by a search engine for the frequent re-spidering of the webpage if it meets with the search engines' quality requirements.