Angostura is a large company with a wide range of products. They're, perhaps, most famous for their bitters--an aromatic that is featured in many recipes including the famous and exquisite Manhattan. They also carry a line of rums (as well as owning a series of scotch and cognac labels.
Angostura rums are distilled in Trinidad from molasses. Trinidad Distillers themselves make other labels of rum, including the ubiquitous Bacardi.
The Angostura Light rum is part of the "butterfly collection" named for Trinidad's collection of 8,000 species of butterflies. Unusual for silver rums, this one is a blend of rums aged between 3 and 8 years in American oak bourbon barrels and then filtered in charcoal.