Search Engine marketing (SEM) is paid marketing within search engines. 

Pay Per Click (PPC) is an advertising method used on search engines, advertising networks, and content websites/blogs, where advertisers only pay when a user actually clicks on an ad to visit the advertiser's website. Advertisers bid on keywords or search terms which they believe that people will type into a Search Engine entry box, when shopping for the goods or services that they sell or  provide. When a user types a keyword search  matching the advertiser's keyword choices, or views a page with relevant content, the advertiser's ad may be shown. These ads are called a "Sponsored link" or "sponsored ads" and appear next to or above the "natural" or organic results on search engine results pages..

Pay Per Click (PPC) Is Paid Placement Services
 

Most of the time, businesses want  multi-engine PPC services. This is bidding on keywords across several different search engines. By using multiple search engines, they are able to take advantage of many keyword bids and get the best result for their money.
 

Google PPC Management

February 2008; Microsoft general counsel stated that they had catalogued Google’s market share percentages both in search and online advertising. He stated that Google “has amassed 75 percent of paid search revenues worldwide and its share continues to grow” and that it currently “has more than 65 percent search query share in the US and more than 85 percent in Europe.”

He estimated that a purchase of Yahoo! would offer Microsoft only an immediate “30 percent combined (share) in the US and approximately 10 percent combined in Europe.” In December 2007 Google exceeded 75%.

Google rules for search. If a  clients want to start off with just one search engine, Google is almost always the best choice, their searches account for about 65% or more of the  American market.

Yahoo (Overture) PPC
 

Yahoo Search Marketing (formerly Overture) is the PPC engine behind a LOT of great website search, including Yahoo, CNN, Alta Vista, InfoSpace, Alltheweb and many others. Roughly 80% of all active internet users use Yahoo-powered websites at least once a month. about 165 million ads are served up by Yahoo Search Marketing per month.

 

MSN PPC
 

MSN PPC is a new from Microsoft. They have a different way of reaching your target audience, and doing keyword research. Some people find the MSN clicks actually results in more final sales. The MSN user may be from a higher income level.

 
 Level Two PPC
 

This refers to more specialized and smaller search engines, like SearchFeed, ABC Search, Search 123, Enhance, GenieKnows, Business.com, 7Search, and others. Although many of these PPC engines are honest and hardworking, click fraud is a significant issue here, with professional fraud artists/affiliates exploiting the engine relentlessly. We rarely recommend these until such time as they fix their problems.