SEO (Search Engine Optimization) involves various strategies and techniques to improve a website's visibility and ranking on search engine results pages. Web development plays a crucial role in SEO as it ensures that the website is technically optimized for search engines, such as having clean code, fast loading speed, mobile responsiveness, and user-friendly navigation. Content writing is another integral part of SEO as it involves creating high-quality, relevant, and optimized content that attracts and engages the target audience, while also incorporating relevant keywords to improve search engine rankings. Therefore, SEO includes both web development and content writing to achieve optimal results.