The Death Star is a space station created by the Galactic Empire to be the most powerful force in the galaxy. With the Death Star they had the ultimate weapon able to destroy an entire planet as demonstrated in its successful test firing on princess Leia's home world of Alderaan at full power and the prison planet of Despayre at half that power.
Commanded by Grand Moff Tarkin of the Galactic Empire with a crew of over 250,000, the Death Star can house around 700,000 personnel once: gunners, troops and support staff are included, It also boast an impressive arsenal including: TIE Fighters, strike cruisers, blast boats and assault shuttles. It also has defense weapons ranging from turbo blasters to ion cannons and tractor beams.
The Death Star was created by George Lucas. It's first appearance in media was the massively-loved Star Wars Episode IV: A New Hope. It's first appearance in a comic book is Marvel Special Edition Featuring Star Wars #2.
Death Star II
After the first Death Star was destroyed the Empire started construction of another one almost immediately. During the battle of Endor the second Death Star was half complete but already had the laser and much of its defenses fully operational. After Han Solo destroyed the shield generator, Lando flew the Millennium Falcon to the very core and destroyed the Death Star's heart, reactor core.
The Death Star has many different turrets, gunners and ion cannons made for defense of its outer skin from attack.
It also contains a myriad of hanger-bays housing just about every conceivable weapon of war in the Empires arsenal for deployment.
It is also equipped with a state of the art shield, through which no spacecraft or weapon of any destructive power may pass and do it any significant damage. The first Death Star had a tractor beam that was powered internally that could be used offensively. The battle of Endor took place as the unfinished Death Star II was unable to protect itself at that stage and was reliant on the shield array base on the forest moon to supply its protection.
The main cannon its self was without equal in the Star Wars universe for sheer destructive power. Able to obliterate a planet with very little preparation or warm up period it did require several minutes cool-down/recharge time when engaging multiple targets such as capital-ships.
The Death Star appears very slow moving both on its own axis and what might be called forward propulsion with no visible means of that propulsion. It does beg the question when facing it the forces always face its cannon rather than attacking from the opposite side (other than for visual and aesthetic reasons of course).
Much in the same way the AT-AT is a hammer blow against an opposing force its size is also its weakness. While Ion torpedoes can penetrate the outer skin and cause internal damage, due to the sheer scale of the station, they have little impact when undirected.
The first Death Star was destroyed because it had a small exhaust port that linked the outer skin with the core reactor and the missiles were delivered directly into it. The second Death Star's weakness was its gaping unfinished super structure allowing passage of Rebellion craft directly down to its reactor core where they fired directly into the reactor itself. this was possible once the shield on Endor was shut down, allowing access inside.