There are two main types of grouts commonly used in construction - Class A and Class C. Both types of grouts are referred to as "non-shrink" as they contain different systems to compensate for shrinkage (as occurs with cement - which is why concrete shrinks as well).
Class A grout contains systems that are designed to counteract shrinkage in the plastic state, usually by gaseous expansion. The plastic state is before it has cured, in which water is evaporating. An example of a Class A grout is Bostik Flowfill GP. Class C grout contains systems that are designed to counteract shrinkage in the plastic and hardened state. They are often specified for precision grouting jobs.