Compared to most Japanese knives the Santoku is a modern invention. Its history began in mid-century, post World War II Japan.
Initially developed as one of Japan’s first all-purpose knives that seeks to perform all of the tasks of the specialists knives such as the Gyuto (originally for beef), the Nakiri (for vegetables) and the Deba (for fish).
Most notably the Santoku has a “sheepsfoot” blade profile where the tip curves down towards the edge at a 60 degree angle, giving it an aesthetic of a gentle blade geometry.
This knife was at its outset developed for domestic use as it privileges control over length of blade.
Distinguishing itself from other chef’s knives such as the Gyuto, the Santoku has a shorter blade length allowing for greater control especially for users with smaller hands.
Today it has a reputation of being a reliable general-use blade that is known for its ease of use.
Purpose & Use
The Sanoku knife is the second most popular knife in Japan (after the Gyuto). It's a light weight all purpose knife with a shorter blade when compared with the Gyuto knife.
The shorter blade length brings the hand closer to what it is cutting making intricate work more easy to complete and moving the elbow forward to allow slicing and chopping.
The Santuko also has less curve (on the bottom of the blade) than the Gyuto making it more suitable for chopping than rolling. Chopping is the fastest and most efficient movement when preparing onions, garlics, etc.
Much like the Gyuto it's not the best at anything but the second or third best at everything.