What is human resource and why it is the major department of any company ?

Human resources is the set of individuals who make up the workforce of an organization, business sector, or economy. "Human capital" is sometimes used synonymously with human resources, although human capital typically refers to a more narrow view (i.e., the knowledge the individuals embody and can contribute to an organization). Likewise, other terms sometimes used include "manpower", "talent", "labor", or simply "people"