Alcohol is a mood-changing drug and both a depressant in larger doses, and a stimulant in smaller quantities.
Alcohol can lower your inhibitions (make you do things you wouldn’t usually do) and could make you feel affectionate, horny, sexually confident, sexually assertive, or keen to experiment sexually. The numbing effect of alcohol can make it harder to climax (cum), and heavy drinkers can lose both their sex drive (wanting to have sex) and their ability to get an erection (hard-on).
Alcohol affects your judgement which can make you more likely to take risks during sex. It can even make you unable to remember what sex you had, or who you had sex with.