SEO (Search Engine Optimization) is the process of optimizing a website to improve its visibility in organic search engine results. This includes optimizing content, HTML, and other elements to make sure the website is properly indexed and ranked by search engines.
SEM (Search Engine Marketing) is the process of using paid advertising to increase visibility in search engine results. This includes using pay-per-click (PPC) ads, paid search engine listings, and other paid marketing tools to increase visibility in search engine results. SEM is often used in conjunction with SEO to maximize visibility and reach.