Welcome to Gensokyo. Here's your complimentary sake and 111 year old girl.
Touhou Project is a series of 2D (with 3D background) vertically-scrolling danmaku shooting games made by Team Shanghai Alice, with three fighting game spinoffs co-produced with Tasogare Frontier. They are similar to regular shooting games, but focus more on weaving through complex patterns containing anywhere from dozens to hundreds of bullets. Every game in the Touhou series is set in the fantasy land of Gensokyo, and the series is known for its huge cast of characters, well-developed storylines, and related materials such as music CDs, fan-made comics and animated videos made to the music.
About Touhou Wiki
This is a wiki for material related to the Touhou game series. Everyone is welcome to WHOOPS, highlighted too far. Silly me.
Everything that I put down so far is the best way to explain what Touhou is basically. There's a lot more details that I can add, but most of the fun consists of finding things out for yourself!
Go nuts, kiddo.