The previous article mentioned the similarities between SEO and SEM, but this time I will compare the differences between the two. 1. In the search results of SEM, the mark of "advertisement" or "Ad" will appear to indicate that the search result is a paid search engine marketing; while SEO will not have any signs such as "advertisement". 2. SEM search results can display additional advertising information, which can be used as supplementary information to make the advertising content more substantial and rich; while SEO will display selected summaries, Google will search for various answers through programs and select the most suitable content from them. Displayed on the search results page as a specific field. 3. Whenever the user clicks on the SEM advertisement content on the SERP, the system will charge a fee, and the merchant can make a bid according to the situation; while SEO is free, relying entirely on website optimization to improve ranking.