What is the difference between SEO and SEM

Seo is search engine optimization and is the process you use in getting your pages to place well on search results. SEM is search engine marketing and involves purchasing advertising space on search result pages. Sponsored listings are SEM. Both are related though! When using Google Adwords, the better you optimize your pages for search, the less you will be paying for your selected keywords in the PPC campaign and the better placment your ads will get.