Fish are abundant in the sea and in fresh water, with species being known from mountain streams (e.g., char and gudgeon) as well as in the deepest depths of the ocean (e.g., gulpers and anglerfish). They are of tremendous importance as food for people around the world, either collected from the wild or farmed in much the same way as cattle or chickens. Fish are also exploited for recreation, through angling and fishkeeping, and are commonly exhibited in public aquaria.

Fish have an important role in many cultures through the ages, ranging as widely as deities and religious symbols to subjects of books and popular movies.