Difference between SEO,SEM and SMO?

[nisha]

SEO-It improves the rank of webpage resulting it on Google, Yahoo, Dogpile, etc and provides organic result.
SEM-In it,we pay for our ad so that it may show within the special sections of the page reserved for advertisements on search engines.And also SEO content is more permanent than SEM.
SMO-SMO is the analysis and strategy creation of what platforms (Facebook, Twitter, etc.) are and/or should be used and how they are being used for paid marketing.