Piggy banks are traditionally ceramic containers shaped like a round pig with a slot in the top for change or occasionally paper money. Some piggy banks have a plug in the bottom allowing money to be retrieved, while others must be smashed for the money to be recovered.

Piggy banks are so named because of a Middle English word, pygg, which describes a type of clay commonly used for making money vessels. Originally, these were simple ceramic pots in which money would be kept, but as the word changed to be pronounced more like pig, ceramicists began making the containers in the shape of the animal. A perhaps apocryphal story tells of a specific potter in the 18th century who received a large order for pygg jars and misunderstood the request, creating all of the jars in the shape of the animal. When the jars sold out quickly from his retailers, other manufacturers adopted the practice.

In modern times, piggy banks come in a variety of shapes and sizes. Many adopt the shapes of other animals, with the cat as the second-most-popular animal represented, particularly in Japan. Other modern piggy banks abandon the animal likeness entirely, relying instead on geometric shapes.

While ceramics are the classic material for piggy banks, most modern piggy banks are made out of plastic, with others made out of glass, steel and even precious metals not uncommon. Plastic piggy banks have the benefit of being more durable than their ceramic counterparts, and may be transparent so the amount of money inside can be easily discerned. The Money Savvy Piggy Bank is a particularly popular piggy bank design from 2001, utilizing a transparent shell with four compartments labeled "Invest", "Donate", "Spend" and "Save", giving people an easy, visual way to budget the money they set aside.

Other modern piggy banks incorporate electronic and mechanical components to add features to the simple piggy bank form. These include electronic registers which automatically tabulate how much money is being put in, and even track how much money is removed. Others have automatic money-rolling systems included, so that as change is deposited, it is placed in bank rolls to be traded in for paper money at a bank. Because of the wide range of complexity found in piggy banks, pricing varies widely. A simple plastic piggy bank may cost no more than US$1 or US$2, while an electronic bank fully loaded with bells and whistles may cost in excess of US$200.