People confuse SEO with internet marketing, for the reason that both of them are interconnected, also because the main concepts and techniques are akin to each other. You may ask, if the nature and techniques are the same, why do we have to name them differently? Can not we just call it Online marketing and take a break? Of course we can, but by doing it we will oversimplify the topic. To tell the truth, SEO and Internet Marketing are indeed two different entities. They are related to each other, but Internet marketing is not limited to SEO and SEO is not all what you can call web marketing.
Of course, the most basic and also a necessary for all websites, if you have not optimized your website for the search engine crawlers; you're missing the trick, altogether. Especially if you are running an online business, you can not afford to do that, because no other marketing technique can send as much traffic as search engines like Google, Bing or Yahoo. Although, you can employ most of the techniques yourself but because it takes lots of time and experience to do it properly and because SEO is not something to be compromised, engaging an expert is recommended. When it comes to SEO, you must learn from your experiences because search engines are not going to reveal their ranking factors.
Internet marketing is a more comprehensive and all inclusive term for anything you do to market your website (which makes SEO a sub category of online marketing). If you have to market your website, product or services on internet, you can not (and you should not) solely rely on search engines for your traffic. You must start from scratch, define your business objectives and make a budget, think about your targeted customers, think of all the available options and try to avail as many as you can while staying in your budget, and that include SEO, SEM, e -mail marketing, blogs and social media, social networking websites, and the likes.
Moral of the story:
As you can see you can not ignore SEO but at the same time you can not rely purely on Search engine optimization to do the marketing work for you. Internet marketing is the most composite term used in online business, and it is undoubtedly the most rewarding one too but it also takes lots of efforts, considerable research, experience, experiments, time and other resources. SEO is probably the first step towards successful marketing your website for the world wide web and you can not think of reaching anywhere without doing the basic SEO work for your website.