Basic definitions:

1.2.3. Load-break switch
The load break switch is a mechanical switching device capable of making, carrying and breaking currents under normal circuit conditions which may include specified operating overload conditions and also carrying for a specified time
currents under specified abnormal circuit conditions such as those of shortcircuit.
A load switch may be capable of making but not breaking, short-circuit currents (IEC 947-1). It is capable of carrying (high short-time withstand capability) but not breaking the short-circuit currents.
 

1.2.4. Disconnector/isolator:-

A mechanical switching device which, in the open position, complies with the requirements specified for isolating function (IEC 947-1). The isolating device must disconnect the supply voltage from the whole installation or from part of the installation, thereby for ensuring safety, the whole installation or part of the installation must be completely isolated from all sources of electrical energy. The important factor here is the isolating distance. The isolation of pole to pole or between the incoming and outgoing terminals must be assured, be it with a visible isolating gap or with the help of appropriate internal constructive measures (mechanical interlocking device).
A device meets the requirements of isolating function in accordance with the IEC 947-1 if it provides an isolating distance in the "OFF" position so that the prescribed dielectric strength between the open contacts of the main current path of the switch is assured. Additionally, it must be provided with an indicator which shows the position of the moving contacts. This switching position indicator must be mechanically connected to the operating mechanism in a reliable and robust way. The operating mechanism itself may serve the purpose of the switching position indicator provided in the "TRIP" position it indicates the position "OFF" only when all the moving contacts are in the "OFF" position. A disconnector is capable of opening and closing a circuit when either a negligible current is broken or made, or when no significant change in the voltage across the terminals of each of the poles of the disconnector occurs. It is also capable of carrying currents under normal circuit conditions and carrying for a specified time currents under abnormal conditions such as those of short-circuit.
 

Main switch:-
Every electrical equipment must be provided with a manual main switch which completely disconnects the equipment from the supplies so that cleaning, maintenance or repairs can be carried out or if the machine is to be taken out of service for a longer period of time.

A main switch must meet the requirements of a switch-disconnector in accordance with the IEC 947-3 (load switch with isolating function - see above). It must at least meet the requirements of the utilisation category AC-23.
A main switch is manually operated and must have only one "OFF" and one "ON" position, which are to be clearly marked with O and I respectively.
A main switch must have a visible isolating gap or an unambiguous indication of the "OFF" position of the switch as soon as the gap between the contacts has reached the prescribed isolating distance in accordance with the IEC 947-3.
As long as the main switch do not serve the purpose of an emergency OFFswitch at the same time, it may not have a red operating handle.
It must be possible to lock-out the handle in the OFF-position (as for example with a padlock).
If necessary, it must be possible to interlock the main switch with a door with the help of an interlocking device.

A main switch placed within the reach of an operator must fulfil the requirements of an emergency OFF-switch.
 

Emergency OFF-switch
In the case of a danger to persons or machines, the part in danger or the whole machine itself must be quickly isolated from the supply and brought to stand-still with the help of an emergency OFF-switch.
The emergency OFF-switch must be capable of interrupting the locked-rotor current of the largest motor connected to it and added to it, the sum of the rated currents of all the other loads connected to the same switch.
The contacts must fulfil the isolating function.
The operating handle or button must be clearly visible by the operator from his operating position and must be located within his easy reach.
The operating handle or button must be coloured red. The background or mounting surface must be coloured yellow so that the handle or the button clearly stands out against the background.
The emergency OFF-switch must not disconnect an electrical circuit, which when disconnected may lead to danger to persons or to machines.
It must be capable of carrying continuously the sum of the rated currents of all the loads connected to it.
 

STANDARDS and references:

Why is the plug socket rating 16Amp and not 20Amp?

Why for a plug(feeder) circuit the circuit breaker is 20Amp rated, the wire size is normally 2.5mm, but the sockets in that circuit are 16Amps! What's up with that?