A significant part of the positive psychic energy of the Id is the libidinous drive or desire for sexual pleasure. Freud thought this was an innate drive, affecting people differently at different stages of development. He thought the libidinous impulse centered on a different part of your body at each stage of growth. First, is the oral stage, where children seek out and derive pleasure from food. Then, the anal stage, where they learn to control their bowels and bladders. Finally, the phallic stage, where they seek and derive pleasure from sex.
In the phallic phase, from about three to five years old, children discover the pleasures of the genitals, and gender differences. This comes after a period of latency where the libido is inactive until the genital stage emerges in puberty. Frustration by parents or society can lead to fixations on the associated erogenous zones, such as anal retentiveness.