Vodka has been around for so long that it is essentially impossible to trace its origin. The Polish and the Russians have an age old debate over who claims it as their own invention, though it is widely considered the national drink of Russian. The word itself is even so old that the etymology cannot be agreed upon, though a common theory is that has its base in the Russian and Polish words for water, "voda" and "woda".
Vodka has different definitions worldwide but it is basically a distilled spirit that is rigorously distilled and/or filtered to a high degree to remove impurities. Some definitions even states "odorless, colorless, and tasteless" to their list or requirements.
Vodka can be distilled in either pot or column stills, made anywhere in the world, and distilled from any fermentable sugar. There is heated political debate as to whether the definition should be limited to the more traditional distillates, barley, wheat, rye, and potato.
Aromas in vodka can be subtle. They often have a noticeable character of their distillate, such as fruit and spice for rye, light sweet grain for wheat, etc.
Vodka is colorless. Except in some flavored examples.
Vodka is distilled to such a degree that its flavors are typically subtle. They range across sweet, spicy, fruity, grainy, flavors and texture of the mouthfeel can vary greatly.
Minimum strength depends on the country of origin. Most are bottles at either 40% alcohol by volume of 50%.