Employee onboarding is the structured program that integrates new hires into the organization. It covers three dimensions: administrative (paperwork, systems access), technical (job-specific skills, tools), and social (team culture, relationships). Effective onboarding reduces ramp-up time, improves retention, and builds cultural cohesion. A new engineer who onboards well is productive in 8 weeks; poorly onboarded, 16 weeks. The difference compounds.