Both SEO and SEM positioning aim to improve the position of a website in search engines. However, the investment required is different. SEO positioning requires more time, effort and a budget of maintenance costs that will show future results. Furthermore, SEM positioning makes you pay for every click in your ads. Likewise, the place of work is not the same because the Google Ads are placed on a column to the right of the page, while search results are much more central.
Besides this, we find an important difference in the content. SEO is based in quality and introduces longer texts, whereas SEM ads have a reduced number of characters to achieve the best impact with the minimum of element. Finally, the time is different too. SEO looks for medium or long term, but SEM is focused on obtaining results more immediate or short term.