Search engine optimization (SEO) involves improving the volume or quality of traffic from search engines to a website. Search engines use software called crawlers or spiders to scan the web and index all pages they find. However, with over 20 billion pages on the web, spiders may not visit a site for months. Effective SEO involves keyword research, competitor analysis, on-page optimization, and off-page submissions like blog comments, article submissions, and link building. Proper SEO can increase traffic and conversions for a website.