What is libido?

libido
lɪˈbiːdəʊ
noun
noun: libido; plural noun: libidos
  1. sexual desire.
    synonyms: sex drive, sexual appetite, sexual passion, sexual urge, sexual longing;

    sexual desire, desire, passion, sexiness, sensuality, sexuality, lust, lustfulness, carnality, eroticism, ardour;
    informalhorniness, the hots;
    informalrandiness;
    rareconcupiscence
    “in men, heavy drinking can result in loss of libido”
    PSYCHOANALYSIS
    the energy of the sexual drive as a component of the life instinct.
    Origin: early 20th century
    from Latin, literally ‘desire, lust’.