Human Capital is the "big umbrella" concept which could include all people, processes, systems related to employees. Human capital is the knowledge, skills and abilities that add value to an organization. Without value then, how can your people truly be considered a part of "capital" (which relates to financial assets).
Human Resources are the function within the company responsible for managing Human Capital, Talent Management: The group and their processes within HR that are responsible for talent acquisition (staffing), talent development (T&D), retention, and succession planning.
Human Resource vs. Human Capital vs. Talent Management: Human resources have two definitions: one is the function within an organization responsible for administering to people and the other is the actual resource of people. Human capital is the skills, knowledge, and experience gained in an organization by people that represents a value investment or resource to that organization. Talent management is the practice of identifying, acquiring, developing, deploying, and retaining well-qualified people throughout an organization and manage business culture as well. It’s an organization's commitment to effectively managing the flow of talent to achieve an organization’s goals. (Activities include: planning, identifying, developing, deploying and retaining)
Some say, HR should give the human capital a tangible "face" in order to setup a connection to the business strategy. By clarifying these concepts, businesses can manage their most valuable asset –people and talent management life cycle more holistically and systematically, also strengthen the weakest link-people between business strategy and execution.