Poop deck is a term used in a naval architecture to define the roof of the cabin on the back part of the ship. The word ‘Poop Deck’ is derived from the Latin word puppies and French word la poupe. A poop deck is essentially the stern deck of the ship. In a sailing ship, this poop deck is usually elevated from the roof. It is therefore easier for the captain or the sailor to have a view of the crew and have better navigation.
Most modern ships, now a days, have a raised bridge area for the purpose of navigation. Earlier, the poop deck was used for these purposes. The cabin below such roof is known as a poop cabin, which was essentially used as a mess for the officers, as well as to store various items like office logs, maps, and so on. The captain, if not found on the helm, would be found on the poop deck, giving orders to the crew. Similar to a poop deck, there is also a poop machine.
Over time, as sails starting giving direction to the engine of the ship, the use of such poop decks dropped significantly. Every common, thereon, was given from the raised bridge, which is being used for multiple purposes. You will still find a raised cabin in some of the modern ships. However, it is just to give a similar look to the old ships, and is not used for anything more than having a sunbath or any other recreational activities.