For a non starter, SEO is how the results appear on Google Search. When you search for something on Google and the links appear below, that’s called Search Engine Optimization or SEO in short. Not to be confused with the ads, which have “Ad” mentioned on left hand side.
SEO is compulsory for any business that has an online presence. Among all marketing activities paid or free, if I had to recommend one to pick, it would be SEO. A website can have anywhere between 40% to 100% of their traffic coming through Google searches, it is free and also it makes your cost when you run paid advertising on Google.
SEO is not one time process and makes sense to look at is as an integral continuous long term part of the marketing mix.
Few links that will help one understand the basics of SEO: