A surge protection unit and an automatic voltage regulator are the same function?

Automatic Voltage Regulators attempt to increase or reduce the voltage in response to a change in input voltage, such that their output voltage is constant. They work by switching a transformer on or off as the input voltage rises or falls. Keep in mind that they often have a very small range within which they can increase or decrease the voltage. For example, a cheap device may only be able to increase or decrease the voltage by a maximum of 10%. They also often have a maximum power or VA rating, e.g. 600 Volt Amps. Unlike surge protectors, they have an unlimited life expectancy (i.e. they are not consumable) as long as you stay within their rated voltage and power (or VA).

A surge protector, like the type you find built into power strips, usually consist of what are called Metal Oxide Varistors. They are devices which shunt high voltage spikes to prevent them from entering or damaging your electronics. They have a limited lifespan, usually specified as a total energy that they can absorb before they no longer work. 600 to 2000 joules is not uncommon. Surge protectors do not effect the voltage level supplied, only fast high voltage spikes.

What is the difference between Overcurrent protection and Overload protection?

Many surge protection devices and installations, have two different working methods: an active automatically resetting component, like a polysilicon fuse, or VDR, and also they might have fuses, physically to be replaced afte surge. While a voltage regulator is a continuous providing service device, who might or not whitstand a surge, depending on specs.

A surge protection unit and an automatic voltage regulator are the same function?

No, they are sometimes tied together in some devices. But they are not the same thing. Voltage regulator is a device weigh held the output voltage constant, over a wide (or not) input conscious. A surge protection is meant to avoid precisely a surge, which mostly destroys your devices/and or installation, like a overvoltage or a lightning hitting the cables.

To summarize: Surge protectors help prevent against very short duration, very high voltage spikes. Automatic voltage regulators help to prevent damage to electronics by increasing or decreasing the voltage over a long period of time. Often Automatic voltage regulators contain surge protectors.