The biological definition of sexual intercourse/penetrative sex is when the male penis enters the vagina. But 'sex' is defined differently by different people. Mouth, breasts, hands and other sensitive areas can bring sexual pleasure and some people think that activities using these parts of the body are also part of sex. Whatever you believe it is, delay sex until you feel ready for it and are in a trusting relationship. Being in a relationship does not mean you need to have sex. You can get pregnant, HIV/AIDS and other infections from oral, vaginal and anal sex so test with your partner and use condoms to protect yourself.
Attribution: Straight Talk Foundation