They appear as low, horseshoe-shaped mounds, typically found near water, and are generally dated to the Bronze Age, roughly 1500 to 500 BC. The mounds themselves are the accumulated debris of repeated use, largely made up of fire-cracked stone. The accepted explanation for most of them is that they functioned as outdoor cooking sites, where stones were heated in a fire and then dropped into a water-filled trough to bring it to a boil. One such site survives at Carrowmeer in County Clare, a quiet addition to a monument type that appears in almost every county on the island.

The name fulacht fia translates loosely from Old Irish as something like "cooking pit of the wild" or "cooking place of the deer", though the exact meaning has been debated. Whatever the precise translation, the association with outdoor, communal, or seasonal cooking is broadly accepted. The characteristic mound shape comes from the waste material, broken and heat-shattered stones discarded after use, building up over time around the trough. Clare itself contains numerous examples, reflecting the county's dense prehistoric settlement, and the Carrowmeer site represents one local instance of a practice that was clearly widespread and long-lasting.