AIDS is acronym for Acquired Immunodeficiency Syndrome. It is an incurable disease who first appeared in Africa and then in USA. It is caused by a retrovirus called HIV.
It is a disease that affects Immune System. It invades white globules and prevents them to do their duty. The affected person then can suffer of multiple infections, called opportunity infections, because they are not caused directly by HIV. These diseases are Kaposi's Sarcoma among others. The person finally dies.
The virus propagates through contact with blood, sexual liquids and from a pregnant mother to her baby.