Sexual arousal (also sexual excitement) is the arousal of sexual desire, during or in anticipation of sexual activity. A number of physiological changes occur in the body and mind as preparation for sex and continue during it. Genital changes are not the only changes but noticeable and necessary for consensual and comfortable intercourse. When men are fully aroused they typically get an erection. When women are aroused, they typically get engorged sexual tissues (nipples; vulva; clitoris; vaginal walls) and vaginal lubrication (wetness). There are mental stimuli and physical stimuli such as touch and the internal fluctuation of hormones which can cause a person to become sexually aroused.
Sexual arousal has several stages and may not lead to any actual sexual activity, beyond a mental arousal and the physiological changes that accompany it. Given sufficient stimulation, sexual arousal in humans will typically end in an orgasm; it may also be pursued for its own sake, even in the absence of an orgasm.
Read more about Sexual Arousal: Terminology, Erotic Stimuli, Sexual Arousal Disorders, Physiological Changes, Psychological Changes, Assessment of Genital Arousal, Category-specificity, Concordance, Hormones, In Other Animals, Evolutionary Models