Hope this helps.
References :
http://teasastipstechniques.blogspot.com
http://www.seomoz.org/article/search-in-china

Visit:-

http://trends.google.com
http://sem.smallbusiness.yahoo.com/searchenginemarketing/marketingcost.php

Regards

… earn more
References :

1. Having Keyword rich web pages

2. Having Keywords in the title of your pages

3. Having Keywords in your domain name

4. Naming the images in your site using keywords

5. Naming the Alt tags of images using keywords

Search Engine Marketing is the process and the methods used to promote your site to search engines. The most common tools are:

1. Search Engine Optimization

2. Article Marketing

3. Video Marketing

4. Social Network Marketing

5. PPC, or Pay Per Click Advertising

In most of these methods, the idea is to generate high quality, relevant content that is keyword rich and placed on sites other than yours, This content contains back links that point back to your site. Google and the other search engines use these factors to rank you in the search results people enter. The more back links you have from original quality content, the more important and relevant you are to Google’s results and page rankings.

The important parts above are that the back links to your site must come from relevant, original content. If you have used some of the spamming services or link farms to try to build your back links, Google may penalize you and possibly even black list your site.

Back links generated "Organically," meaning that they are from high quality, relevant content are also very important to Google, whereas Paid advertising – even Google’s own PPC program – does nothing to help you get higher up in the page results rankings.
References :
http://www.higherimages.com

Pay per click:
is when a website pays a search engine for every click they get on their link, this way the search engine puts their website on top of the search list since it is more likely the person will click on it. Google also is an example of this, for example search "lawyer in miami" the first links will be lawyers who pay google for every click they get, so google puts them on top as they are more likely to get clicked there. ( but also google not only puts them there for their money but for the quality of their website too. that is what the rating is for)

hope this helps you.
References :
you can also look at it here, they explain it well in this website:

http://en.wikipedia.org/wiki/Pay_per_click

http://en.wikipedia.org/wiki/Search_engine_optimization

SEM (Search Engine Marketing) falls into two primary categories: pay-per-click and pay-per-impression.
Pay-per-click is just like it sounds, paying a search giant to deliver actual click of an advertisement that leads to your website.
Pay-per-impression is a little more cryptic; it means paying a search giant to get views of you advertisement.
Taking Google as an example once again, you can setup ppc advertisements as suggested links whenever a search of specific keywords is performed.
I am not familiar of how Google (or any other search giant for that matter) handles ppi ad campaigns.
References :
Personal Experience
Friends and Colleagues that have dealt with SEO and SEM