I want to point out the similarity between the two.
Search Engine Optimization (
SEO) is done on-site and off-site, to get your page ranked in the natural listings.
Pay Per Click (PPC) is paid advertising, but if you want to spend as little as possible on each click, you need to also use
SEO.
A part of on-site
SEO is putting your targeted keywords in the content of your webpage. Specifically the title and first few paragraphs. If you make sure to have these targeted keywords in your content, then they will be cheaper for you in PPC. If you are bidding on keywords that are not in the content of your page, they will be more expensive for you than another page that does have those keywords.
So,
SEO is also important for PPC.