SEO - Search Engine Optimization, is a programming or coding service to raise the ranking of your targeted keywords on Search Engines like Google, Yahoo, Bing, Baidu, etc.. Keywords land on the free search result zone and will have no charge from Search Engines no matter how many clicks your visitors make.

SEM - Search Engine Marketing, is to place your keywords or banners at the paid zones of Search Engines or Forums including Google, Yahoo, Bing, Baidu, discuss.com.hk, uwants.com, etc.. Advertisement is pay per click or pay to unlimitedly display. You can set budget per day to avoid being over charged.

Email Marketing is the best way to spread your message to your targeted audiences through emails. You can create a nice email template and then send it to a list of recipients which you stored. Sending mails cannot be charged per email address while it is usually the most cost effective and has the fastest influence.