Power conditioning is a general term that includes a lot of things.
Your audio and video equipment expect to be fed with 220 volts at 50Hz. Power units inside the equipment, in turn, use this power to convert to DC voltage or any other form that they require.
The power that is supplied to you by the electricity board has various issues. The voltage may become low or high. This may be for some continuous period. A servo controlled stabiliser senses the voltage coming in, uses a transformer inside, and converts the voltage to 220 volts. This is called a servo, as the sensor drives a motor that moves a coil inside the transformer to give you the correct voltage. Such stabiliser also have large capacitors that store the power that you need to supply it to you.
Stabilisers are used when there is long term shortage or surge in voltage.
Power supplied by the electricity department also have spikes and surges which are of very short nature. If the voltage jumps to, say, 500 volts for a few microseconds, this is called a surge. A surge is controlled by a filter that simply blocks the surge from reaching your device. Similarly when the surge is of a very large quantum such as, say, 20,000 volts, this is called a spike. Again a filter mechanism is used to block spikes.
Surge and spike suppressors are passive devices - they are simple filters that just block beyond a certain specified limit. They are inexpensive to make.
Low or high voltage can also occur for long periods of time. This requires an active device that generates more voltage or reduces the voltage. This is done by the stabiliser.
Stablisers from companies such as Vertex, Krykard, Aplab also come with surge and spike suppressors built in. You can specify this requirement when ordering.
Unless you have steady and dependable voltage being supplied to you continuously, it is better to protect your equipment with stabilisers.
Stabilisers, surge suppressors, UPS, Inverters are all together called power conditioning equipment.
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