Doraemon is sent back in time by Nobita Nobi's great-great grandson Sewashi to correct Nobita's bad circumstances so that his descendants may have a better life in future. In the original timeline, Nobita experienced nothing but misery and misfortune throughout his life. As a result of this, Nobita's failures in school and subsequently, his career, have left his family line beset with financial problems. In order to alter history and improve the Nobi family's financial status, Sewashi sent a robotic cat called Doraemon.
The stories are formulaic, usually focused on the everyday struggles of fourth grader Nobita, the protagonist of the story. In a typical chapter, Nobita comes home crying about a problem he faces in school and/or the local neighborhood. After hearing him out, Doraemon always offers helpful advice to his problem(s), but that's never enough for Nobita, who is consistently looking for the "quick, easy" way out (which offers insight to the viewers as to why Nobita's life turned out the way it did). Finally, after Nobita's pleading and/or goading, Doraemon pick a gadget or tool from a future department store out of his aforementioned pouch to help Nobita fix his problem, revenge, or flaunt to his friends.
Nobita usually goes too far, despite Doraemon's best intentions and warnings, and gets into deeper trouble than before. Sometimes, Nobita's friends (usually Suneo or Jaian) steal the gadgets and end up misusing them. However, by the end of the story, there is usually retribution to the characters who end up misusing them, and a moral is taught.