The southern Caribbean islands form the lower portion of the lesser Antilles (the main Caribbean islands arc), along with Netherland Antilles (Aruba, Curacao, and Bonaire), Barbados and Trinidad & Tobago.
People often refer to the four islands in the arc as the Windward Islands, because they face the trade winds directly, giving them a near constant breeze to cool you on a hot Caribbean day.
The southern islands include:
The southern (particularly the Windward) Islands arise from the ocean where the Atlantic and Caribbean tectonic plates meet, and are actually the tops of a volcanic mountain range (and here you were thinking that Hawaii was the only volcanic islands in the Americas). In fact, three of the Windward Islands actually have active sulfuric vents, the exception being Grenada, where they have hot springs.
Because of their mountainous terrain, these Caribbean islands ensnare the trade winds blowing off the Atlantic. This trapped wind helps to create rain, which keeps these islands particularly lush and fertile. In the higher elevations, there are dense rain forests with bountiful, beautiful vegetation and animals.
Most of the major cruise lines have ports of call in the southern Caribbean, with Carnival and Royal Caribbean offering trips to this area of the Caribbean islands nearly every month of the year.