Question

why is money considered as a mediam of exchange?

Answer 1

its because money is accepted in all regions or its the only way we we can buy any goods and services 

money helps to avoid cheating 

Answer 2

money is accepted as a medium of exchange because it is authorized by the government of the country.
In India, the Reserve Bank of India issues currency notes on behalf of the central government. As per Indian law, no other individual or organisation is allowed to issue currency. Moreover, the law legalizes the use of rupee as a medium of payment that cannot be refused in settling transactions in India. No individual in India can legally refuse a payment made in rupees. 
the double coincidence of wants as we required in the barter system. that problem is also solved by money.
hence, the rupee is widely accepted as a medium of exchange in India.