I am also interested who and how decides its value?
A pip (percentage in point) is the smallest increment in a currency pair, in 4 digit brokers. Nowadays, with 5 digit brokers, those are called pipettes. But for the sake of simplicity, let's assume a pip is the smallest price increment quoted to the fourth decimal point in the forex market.
In finance, specifically in foreign exchange markets, a percentage in point (pip) is a unit of change in an exchange rate of a currency pair.
Pip means "Price interest point". Is the 0.0001 or 0.01 price change
This minimal change price distance.
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