A fountain in heraldry is not usually a stone structure with water spraying, but a stylized roundel: a circle barry wavy argent and azure, typically shown with six wavy bands, three silver (white) and three blue. In English blazon, the plain word fountain (or the older term syke) means this conventional charge, and artists are expected to draw the wavy-striped roundel rather than a “real” architectural fountain (Wikipedia: Fountain (heraldry); Mistholme: Fountain). If a designer truly wants an edifice, blazons often specify a “natural fountain” or similar wording, which shifts the charge from symbol to structure.

Symbolically, the heraldic fountain speaks to fresh water, springs, wells, and life-giving supply, so it suits communities defined by rivers, aquifers, or notable springs, and it can suggest renewal, healing, and sustenance. It also has a technical heraldic charm: because it is evenly composed of a metal (argent) and a colour (azure), it is commonly noted as not constrained in the same way by the rule of tincture as a single-tincture roundel would be (Wikipedia). That makes it a useful, legible “water” emblem that can sit on many fields without visual clash.

Real usage often follows local identity or wordplay. Wikipedia lists civic examples including the former Finnish town Anjalankoski, County Leitrim in Ireland (three fountains), Götene Municipality in Sweden, and Nairobi in Kenya, and it notes canting arms such as Fontenay-le-Fleury and Il-Fontana in Malta (Wikipedia). For image browsing, start with Wikimedia Commons: Heraldic fountains in heraldry, and for a classic definition reference see Berry’s 1810 manual via Google Books.