Fireplaces are small campfires created by players for the purpose of cooking Raw Meat. To create a fireplace, the player must have a Wood Pile in their main inventory and a Box of Matches. The fireplace is created by right-clicking on the Box of Matches and choosing the "Create Fireplace" option. This places a fireplace at the player's location, which can then be lit by choosing the "Light Fire" option from the mouse wheel menu.
This page contains information about the mod version of DayZ. Standalone information is available here.