These materials are used in large quantities as building and engineering materials (including limestone products, concrete, and mortar), and as chemical feedstocks, among other uses. The rocks and minerals from which these materials are derived, primarily limestone and chalk, are composed primarily of calcium carbonate. "Burning" (calcination) converts them into the highly caustic material quicklime (calcium oxide), and, through the addition of water, into the less caustic, but still strongly alkaline slaked lime (calcium hydroxide).
In general writing when the term is used in an agricultural context it probably refers to Agricultural lime. Otherwise it most commonly means slaked lime, as the more dangerous form is usually described more specifically as quicklime or burnt lime.