Difference Between Search Engine Opimization and Search Engine Marketing

SEO Vs SEM
Search Engine Marketing

I see SEM as a rather broad Field. SEM is the common use of marketing methods designed to create a website more visible to Google and other search engines. These methods include paid search methods, such as Google Ad Words purchases, pay-per-click advertising.In this system, anyone can bid to have their ad shown next to the organic search results for specific keywords.
Currently Google shows these sponsored ads on the side and (usually) the top of the organic results.Search Engine Marketing is more wide than Search Engine Optimization, because it itself includes optimization along with all marketing strategies(paid and non paid).

 SEO, however, is an organic search (Free Seo) marketing method used to rank a website higher in search engine without paying to search engines.Feeding your website with fresh and unique content on a regular basis will improve slowly (but surely) your rank in the search engine results. You just have to make sure that your keywords are unique and are seamlessly placed in your content.

In simple words SEM = Search Engine Marketing. It includes seo (nonpaid) and paid techniques like paid inclusion and paid placement.

SEO = search engine optimization. optimizing your site for natural listings and directories.seo is a piece of sem.it doesn't include paid techniques like PPC etc.you dont have to pay any penny to any search engine to rank your web high in search results.SEO, therefore, would be a subset of SEM.

if seo is done properly you don't have to pay google/altavista(MSN),Yahoo to rank your web against certain keywords as it will be already on the top or 1st pages of search engines and getting terrific without using SEM.