- seo is organic way to rank website traffics and rank keywords.
- SEM is paid marketing in google adwords, big ads and yahoo and other paid marketing for keyword and visibility on website.
- SEM is Paid for pay marketing. this main difference.
- SEM is a broader view. Search Engine Marketing.. EITHER PAID or by SEO. SEO is a sub-part of SEM
- sem = ADS, pay google bing or yahoo directly to get more visibility in their ranks seo = no ads. rank in google by yourself, with costs but it depends of each one
