Different types of fires have different characteristics. What they are fuelled by significantly alters how they must be extinguished. The different extinguishers are then located in different areas of the building to ensure that the risks of that area are sufficiently covered.
Any extinguishers over 2kg, and a 2kg CO2, should have their handles mounted at 1m from the floor level. Any fire extinguishers smaller than this, should have their handles mounted at 1.5m from the ground.