How do you define 'SEO in Marketing'?

Search engine optimization is the process of improving the quality and volume of web traffic to a website by employing a series of proven SEO techniques. SEO can be a bit confusing as there is no single, comprehensive approach that works for every website. Just as every company is unique, success with SEO requires that an Internet marketing solutions company draft a unique strategy for each client

1. An SEO Strategy – SEO analysis of your site conducted by an experienced SEO advisor to identify opportunities for improvement and devise a comprehensive approach that will get results.
2. Keyword Research – Thorough research of your industry and identification of which keywords and phrases will achieve the best results.
3. SEO Copywriting – Content optimization using your keywords and phrases in the pages of your site to achieve higher ranking.
4. Link Building – The process of creating inbound links to your website which allows your site to achieve a higher ranking.

These are the basic main aspects of an effective SEO which can be for formulated according to the need and greed of the Industry to be optimized .

search engine optemization is a way to inform any search engine like google , bing ..etc about your website , this mean for more spread to your e-commerce website you must be a very good SEO expert , and to do so you must be an expert at webmaster tools

Disclaimer: I am a digital media professional with experience in digital marketing only. I want to give a different answer.

Since you mentioned 'marketing and not digital, social or online marketing, I am going to assume you are referring to good old traditional marketing.

SEO in traditional marketing would probably be the use of:

1) Buzz words related to the industry the marketing is done for.

2) Trigger words that are used to attract the customer to make the purchase.

How the traditional advertisement foot traffic  (visitors, viewers, POS) convert to buyers, would be your ROI on traditional marketing.