They appear as low, horseshoe-shaped mounds, typically found beside a stream or marshy ground, and are generally dated to the Bronze Age, though examples range from the Neolithic into the early medieval period. The name, loosely translated as "deer roast" or "wild cooking place", reflects one long-held theory about their purpose: that they were outdoor cooking sites, where stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil. Experiments have shown this works remarkably well. The mounds themselves are the accumulated debris of those shattered, fire-cracked stones, discarded after each use.

The example at Ballyline in County Clare sits within a landscape that would have been familiar to Bronze Age communities throughout the west of Ireland, a terrain of low hills, wet ground, and river systems that made such features both practical and plentiful. Clare has a particularly dense distribution of fulachta fia, and while many have been damaged by drainage or ploughing over the centuries, a significant number survive as earthworks. Beyond the cooking explanation, researchers have proposed alternative uses for these sites over the years, including bathing, textile processing, and even brewing, and the debate has never been entirely settled. What is consistent is the setting: proximity to water was not incidental but essential to how these monuments functioned.