Shotokan is the Japanese style that evolved from the teachings of Funakoshi Gichin Sensei.
Shotokan means "hall of Shoto" Shoto being the penname Funakoshi adopted in caligraphic works.
Being a teacher he was the logic choise to demonstrate Karate on the mainland Japan in 1917. During his life Funakoshi Sensei kept editing, rivising and updating the various techniques and bodydynamics until the day he died in 1957. This also explanes why a related style like Wado ryu differs so much from Shotokan.

Shotokan karate, with 16 basic Kata teaches relatively fewer techniques than other styles. Instructors adhere to the concept of teaching a thorough knowledge of a few techniques, rather than superficial familiarity with numerous techniques. Students first learn to assume strong stances and to snap punches without lifting the shoulders. After months of practice a student is ready to intergrate various stances with punching and kicking techniques and to begin moving forwards and backwards while using combination techniques.

During training a large part of the time is spent doing Kata in wich lies the Soul of Karate. Stances mainly used in the basic Kata are the deep rooted onnes like Zen-kutsu-dachi and Shiko-dachi In the more advanced Kata one can see the more lighter stances like Neko-ashi-dachi.
Also in the basic Kata the movements tend to be larger than the ones in the advanced Kata Shotokan is represented by many different organisations, all of whom have a large following thus making Shotokan the biggest Karate style