The plans for the Death Star were originally made by Darthenshmirtz to be a nutcracker, as explained to Norm-3PO, which were promptly taken by the empire and used to make the battle station. Upon completion, the Death Star is taken control over by the Imperial Grand Moff Tarkin and where Princess Leia Organa was sent to following her capture above Tatooine. Seeking to interrogate her about the whereabouts of the Rebel Alliances' main base, he threatens to use the Death Stars' superlaser against her adoptive homeworld of Alderaan if she doesn't reveal the Rebellions' main base. Pressured by protecting her home and her allegiance to the Rebellion, Leia says that the Rebels are on Dantooine (which was actually an abandoned Rebel Base), pleased with the supposed honesty of Leia, Tarkin told to continue with the operation and destroy Alderaan as a public test of the Death Star to show the price of rebellion against the Galactic Empire, citing that Dantooine was by-comparison too remote of a location for a "proper" test. Princess Leia was forced to watch in horror as her homeworld was destroyed.
The Death Star looks like It's film counterpart, except for an added addition: a self-destruct port that was installed by Darthenshmirtz..