What is libido?

In its common usage, libido means sexual desire, sex drive and it's also identified as psychic energy, physiological and emotional energy associated with the sex drive. Sigmund Freud saw the libido as linked not only with sexual desire but with all constructive human activities. And Carl Gustav Jung used the term libido more broadly to encompass all life processes in all species. Many times today it's somehow loosely used to actually mean sexual desire.