A liquor is usually the primary spirit in a cocktail. Liquors are typically distilled and bottled to a higher Alcohol By Volume (ABV) than liqueurs, wine or beer. They are tightly regulated (more so in some states than in others).
Liquor can be derived from grains, fruits, or vegetables, and the resulting product may carry some of the characteristics of the source material. In the case of vodka, the product is highly filtered, or repeatedly distilled to yield a colorless, flavorless product.
Vodka is often produced from potatoes or grains. Whiskey is also distilled from grains. Tequila is commonly distilled from the agave cactus. Rum is produced from sugar cane, or molasses.
Rum changed everything for me with regard to cocktails. Vodka offered only alcohol, but rum offered TASTE.
I realized with the first Martini, that maybe strong savory drinks weren’t my thing.
Rum led to Tiki drinks. Since I have a sweet tooth, it was a good fit for my taste. It goes to reason that a spirit produced from sugar cane would have a sweet character.
Light rum is usually unaged or lightly aged. It is usually presented in the bottle as a clear or nearly clear spirit.
Aged rums have spend some time in a charred oak barrel and some of the characteristics should be in the taste of the bottled product.
Dark rums might have spent some time in a charred oak barrel, but frequently have only had some caramel coloring added.
Rums with various flavors are common.
Spiced rums are made from a rum base with a variety of spice flavors added. Rums with coconut, mango, pineapple, lemon, banana, and other tropical flavors are readily available.