The main goal of SEM is to optimize the visibility of a website within search enginess. SEM based on paid links by choosen key words. The links will be shown within the search enginess as on google on the right side or on top.
Weblinks: SEM Grundlagen
Affiliate marketing is playing along with the classic display advertising and search engine marketing attractive now a huge role in the advertising industry on the web.
For further information click here: Affiliate Programs