what is the different between SEO and SMO? which is more important than other?
Each is important in its own way. There is a lot you can find out about this online. Have you done any research on this? It is better to come here with more specific questions. 
You can not compare SEO and SMO because both are important. in SEO you have to target proper keyword in your page so you can do promote it
SEO - title tags, headings, image title, bold text and the use of keywords are influential in search engine rankings.
SMO - Coding and labels are less important, while visual attention grabbers have a greater impact.
SEO - The title tag of a page tells search engines what is a page and a lot of weight in the rankings.
SMO - The titles and the titles are very important to attract attention and get users to click-through.
According to me, Both are important. SEO and SMO is a different ways to increase your site. In SEO you can do ON page and Off page work. In SMO you can add your business and also provide your business quality. You can do SMO like Facebook, Twitter, My space, Bebo etc…
both are help your website promotion set your page in facebook, twitter and many social media website then relevant keyword your can promote your website.
OK, this looks like another one of those pointless general questions to which the OP never replies, and the answers to which keep saying the same thing. So anyone with the same question should do some online research, as there is plenty of info out there.