The setting is mainly based on the city of Kasukabe in Saitama Prefecture. The main character is Izumi Konata, a lazy girl who constantly blows off her schoolwork and homework, and instead spends most of her time watching anime, playing video games, and reading manga. Although she is lazy, she has shown to be very intelligent and athletic.
The serialization began with the four main characters in their first year of high school: Izumi Konata, Hiiragi Kagami, Hiiragi Tsukasa, and Takara Miyuki. As the story progresses, they move on to their second and third years. However, the anime starts the story with them beginning their second year, and the other high school girls that are seen in the opening are only introduced halfway through the series. The storyline usually includes numerous references to popular past and present manga, anime and tokusatsu series (live-action films or television dramas that make considerable use of special effects).
It is really hilarious, and if you have watched other popular anime series, there is a high chance you will see them referenced here! "The Melancholy of Suzumiya Haruhi" is an excellent example, or would the protagonists' voice actress be the same, Hirano Aya (read about her HERE)!
Here are two funny parts of the anime! Enjoy!