Vodka is defined as a neutral-flavored, clear spirit. At its core, it is supposed to be virtually tasteless, odorless, and clear (like water) in color. But vodka does have very subtle flavors that are distinguishable between brands. Some are peppery, some are creamy, and others have hints of citrus or grain (though it can be hard to pick up on these subtleties even when drinking vodka straight).
Vodka’s subtle flavor makes it an extremely versatile spirit to use in cocktails—its ability to showcase other ingredients’ flavors and aromas is unrivaled because it doesn’t have any (or very little) of its own.
Vodka is generally made from grains or potatoes, but it technically can be made from anything. As long as the spirit is flavorless, odorless, clear, and bottled at 40% ABV, it can be called vodka.