You’re holding a $100-dollar bill. It’s a conventional currency which, owing to its physical nature, can get burned, lost to a pickpocket, or made to disappear through clever hocus-pocus in the bookkeeping.
At least, in theory, this would not happen with a cryptocurrency. It is a digital type of money that, despite having no physical form, acquires value because of the consensus among a network of independent computers to recognize it as legal tender.
Unlike, for example, the dollar or euro that is controlled by a central bank, a cryptocurrency is decentralized. Its transactions are secured by sophisticated encryption techniques so there is no possibility of modification or double-spending.