Double-spending is defined as a form of deceit using digital money where the same money is promised to two parties but only delivered to one. If completed successfully, one of the two recipients will not be paid.
Bitcoin was the first digital money to provide a good solution to prevent double spending.
Bitcoin prevents double spending with a permanent, public and digital book of records known as the blockchain. This blockchain can record any information. Each page in that book can be considered to be a block.
Because the blockchain public, many people are simultaneously verifying and recording information on it using their computers. After enough users in this network confirm your transaction, the guy who wants double spend cannot.