Split AC as the name indicates is designed in such a way that the two key functions of the AC are split into two compartments. One is the hot side, i.e. the compressor condenser unit, and the other is the cool side, i.e. the expansion valve and the evaporator unit.
The splitting of the two units allows one to install the cooling unit inside and the hot noisy unit outside. Since two units are separate individually, they can be larger and thus the AC can be easily designed to be more powerful than windows AC. Window ACs have size limitation and therefore they cannot exceed certain capacity.
Since the compressor condenser unit can be installed outside the building, the room where the AC is installed can still be quiet. Split ACs are an excellent option for office use and for large commercial buildings. Due to their compact size and affordable prices, split ACs have become popular for even household usage.
Split ACs do not work well in case of multi-storied buildings where connecting the room units with the exterior condenser becomes a difficult task.