SEO stands for Search Engine Optimization and PPC stands for Pay Per Click.  SEO is a technique to help optimize your website to appear higher in a search engine results for a given search query.  These are also called “organic” results.  PPC is a type of paid advertising on the Internet where you pay to place your marketing message.  You only pay if someone clicks on your ad.  These are called “paid” results.

https://blog.hubspot.com/marketing/tabid/6307/bid/1514/paid-search-vs-organic-search.aspx