The difference between SEO and SEM is as follows:

SEO (Search Engine Optimization): Focuses on improving a website or page to increase its visibility in organic (unpaid) search results. It includes strategies such as keywords, internal links, and content quality.

SEM (Search Engine Marketing): Includes all activities that use paid ads to appear in search results, such as Google Ads or Bing Ads. SEM also encompasses strategies like text ads, display ads, and social media marketing.

In summary, SEO aims for natural and free visibility in search results, while SEM involves using paid ads to enhance visibility in search results and other platforms.