Melanesia is a subregion of Oceania extending from New Guinea island in the southwestern Pacific Ocean to the Arafura Sea, and eastward to Fiji. 

The region includes the four countries of Vanuatu, the Solomon Islands, Fiji, and Papua New Guinea.
Besides these independent countries, Melanesia also includes: 

The name "Melanesia" (in French "Mélanésie" from the Greek , "black", and , "islands") was first used by Jules Dumont d'Urville in 1832 to denote an ethnic and geographical grouping of islands whose inhabitants he thought were distinct from those of Micronesia and Polynesia. 

The name "Melanesia" ("islands of dark [people]") is one of several toponyms sharing similar etymologies, ultimately meaning "land of the blacks" or similar meanings, in reference to the dark skin of the inhabitants. The concept among Europeans of Melanesia as a distinct region evolved gradually over time as their expeditions mapped and explored the Pacific. Early European explorers noted the physical differences among groups of Pacific Islanders. In 1756 Charles de Brosses theorized that there was an 'old black race' in the Pacific who were conquered or defeated by the peoples of what is now called Polynesia, whom he distinguished as having lighter skin. In the first half of the nineteenth century Jean Baptiste Bory de Saint-Vincent and Jules Dumont d'Urville identified Melanesians as a distinct racial group.
What area of the world is Melanesia in?
Which island starts it?
Which place ends it?
How many countries are in it?
Is Vanuatu one of them?
Which language is the name from?
What does the name mean?
Who created the term?
When?
To label what?
Did he think they were different from other groups?
How many other groups?
What were their names?
Who described these people as different from others?
Who else?
When did de Brosses make his theory?
What did he think had existed?
What happened to them?
By whom?
What was different about the Polynesians?
Oceania
Melanesia is a subregion of Oceania
New Guinea
extending from New Guinea island 
Fiji
 and eastward to Fiji. 
four
The region includes the four countries
yes
 includes the four countries of Vanuatu
French
The name "Melanesia" (in French "Mélanésie
islands of dark [people]
The name "Melanesia" ("islands of dark [people]"
Jules Dumont d'Urville
was first used by Jules Dumont d'Urville
in 1832
first used by Jules Dumont d'Urville in 1832
an ethnic and geographical grouping of islands
 to denote an ethnic and geographical grouping of islands
yes
distinct from those of Micronesia and Polynesia. 
two
distinct from those of Micronesia and Polynesia. 
Micronesia and Polynesia
distinct from those of Micronesia and Polynesia. 
Jules Dumont d'Urville
was first used by Jules Dumont d'Urville
Charles de Brosses
 In 1756 Charles de Brosses
In 1756
In 1756 Charles de Brosses theorized
an 'old black race'
theorized that there was an 'old black race'
they were conquered or defeated
'old black race' in the Pacific who were conquered or defeated
the peoples of what is now called Polynesia
conquered or defeated by the peoples of what is now called Polynesia,
they had lighter skin
whom he distinguished as having lighter skin.