Search engine optimization (SEO) involves making changes to web pages and content to improve visibility in organic search engine results. Key SEO terms include ranking, which refers to a listing's position in search results; search engine results pages (SERPs) which display organic and paid search listings; and bots, crawlers or spiders which index website content for search engines. White hat SEO tactics optimize websites for both people and search engines through best practices like useful content, while black hat techniques try to manipulate rankings through deceitful or unethical means.