HIV stands for Human Immuno-deficiency Virus. After entering the human body, it gradually destroys the immune system.
AIDS stands for Acquired Immune Deficiency Syndrome. It is the later stage of infection with HIV when a group of symptoms appear as the immune system becomes very weak. It can take around 8-10 years from the time of HIV infection to the stage of AIDS. HIV infected people can lead symptom–free and productive lives for years.
HIV can be transmitted through unprotected sex with an HIV infected person, transfusion of HIV infected blood or blood products, sharing of needles contaminated with HIV infected blood and from HIV infected mother to her baby – during pregnancy, during birth or after delivery through breast milk.
HIV is found only in body fluids, so one cannot get HIV through ordinary social contact like shaking someone’s hand, hugging, etc. While HIV is found in saliva, sharing cups or utensils has never been shown to transmit HIV.
Information Source: http://www.indiahivinfo.naco.gov.in/naco/content/faq-hivaids