Over the coming days I’ll be adding more and more definitions for everyone so that when using terminology with you, you are no longer confused 
Search Engine Optimisation (SEO) – The process of ranking well in the free side of the search engine’s. It is a way of coding and keyword structuring a website. See image below for an example on google:
Pay Per Click (PPC) – This is the online advertising system used by some search engines, social media sites and blogs where you pay an amount for every click that you receive on an advertisement. This is often referred to as the pay side of search and can be seen on google in the image below:
Pay Per Lead (PPL) – This is an online advertising system used primarily in affiliate programs (although it was tested on google briefly). This is where the advertiser only pays when they have a defined lead. The advertiser normally has the ability to define what a lead is
Pay Per Sale (PPS) – This is another online advertising system used primarily in affiliate programs. This is where the advertiser only pays when they have an actual sale go through.