SEO stands for search engine optimization and involves techniques to improve a website's organic rankings in search engines like Google. There are three main types of SEO: white hat focuses on user-friendly techniques; gray hat uses some risky techniques; and black hat was risky but is now detected by Google. Key elements of SEO include on-page optimization of content, keywords, and site architecture as well as off-page factors like link building. Hiring an SEO agency can help businesses improve their search rankings and profitability through professional SEO services.