I am going to start with SEO, as it is a part of SEM. SEO is the act of optimising the HTML and other content of your website for relevant, targeted key phrases in order to attain higher natural listings than competing websites. SEO provides a cheaper long term solution for increased qualified traffic and generates customer inquiries that ultimately convert to sales.
Now SEM is broader than SEO. It includes SEO and other areas to improve a sites visibility in search engine results pages, like paid listings and paid inclusions.
You can think of SEM as more expensive and quite possibly more targeted, while SEO is free (not counting your time of course) and its purpose is to obtain better free search listings.
Personally, I would start with SEO and then move onto SEM.
SEO means Search Engine Optimization and SEM means Search Engine Marketing. Both are not same. SEM is the instant approach of advertisement media where as SEO is the longer approach of advertisement media. SEM is the paid listing and SEO is the organic or free listing.
SEO and SEM is different not only by there names but also with the activity, Organic ranking improvement is SEO, and Marketing through Search Engine is SEM.
SEM is all about paid links, advertising more likely on building links
Common tasks you will encounter in a search engine marketing career include managing PPC campaigns, ensuring the income you, or the company you work for, has sales exceeding the amount spent on advertising.
In the SEO subgenre of SEM, you will be building links and promoting your website on article directories, social bookmarking sites and industry-related blogs
SEO is the process of tailoring a website (text, titles, meta tags, alt tags etc…) so that search engines will assign a good rank to the sites for the specific search terms.earch engines introducing fees for guaranteed inclusion in their indices, directories charging for reviews and the emergence of PPC listings, SEO now has an element of media buying mixed in.
The SEM is meant to be both a tutorial and a general information resource.If you frequent other prominent SEM resources you will find that this tutorial, like most search engine promotion sites, tends to go over the same ground. This is because there are no secrets to successful search engine positioning - just experience, a lot of research and tons of hard work.
SEO and SEM are just terms… it’s what you do within those terms that matter. For example, someone may refer to SEO and mean all optimization (paid & organic) while someone else may talk about SEM but only focus on paid. Ask a vendor, get an explanation, and focus on search as a comprehensive strategy.
SEO & SEM both are integral part of Search Engine Optimization. SEM - Search Engine Marketing is the huge concept where as SEO - Search Engine Optimization is one part of it. SEO the process follows are ON-page optimization and Off-Page Optimization. Where as in SEM you do Seo, Paid Optimization ( PPC, Paid Link), E-mail Marking, internet marketing, Social networking optimization, social bookmarking and many more.