Ductless systems allow for flexibility. A single-zone (also called a mini-split) ductless system allows you to control the temperature of one room by connecting an outdoor unit to an indoor unit, with no ductwork needed. An outdoor mini-split unit is placed outside your home and is connected to an indoor mini-split unit by small cables and a refrigerant line through a hole in the wall.
A multi-zone (also called a multi-split) ductless system connects an outdoor unit to an one or more indoor units, letting you control the temperature in several different zones of your home. Variable Refrigerant Flow (VRF) systems are a type of multi-zone ductless systems. VRF systems are energy efficient, and they can be used to heat one zone while cooling a different zone at the same time.