SOCKFIT is a term Adidas use to describe the design of the 'upper' of some of the their running shoes.
The 'upper' section of a shoe is the section that surrounds the foot and is above the midsole of the shoe. The traditional material used for an upper is leather; Adidas has also used canvas, nubuck and suede. The drawback to these traditional materials is their weight, breathability, fit, and 'bed in' timeframe. Therefore, in modern Adidas shoes - like the Pure Boost ZG - Adidas has begun to use a new 'upper' technology, named: SOCKFIT. As the name suggests, it's designed to fit snugly around the foot; just like a sock. The difference between SOCKFIT and a sock is that SOCKFIT has a more stable and thicker construction; ensuring the shoe is durable and does not fall apart like a sock naturally does. The outer layer of SOCKFIT has a web like construction that ensures it's stability and protects the foot from gentle impacts.