STI, STD and venereal disease are different names for the same thing. STIs are passed through sex acts, sharing needles, and mother-to-baby during pregnancy, delivery, and breast-feeding. All sex acts put you at risk of getting an STI. During sex acts, you can get some STIs through body fluids and others through contact. Some sex acts expose you to more STIs than others. Using protection reduces your chance of getting an STI.