Imagine spending 5000 rupees to purchase a new phone online.
Once the phone is delivered, logically you cannot still have those 5000 rupees. You spent the money buying the phone, right?
With a 51% attack, a person is able to to control more than half the blockchain network.
With this control, they can alter the chain’s records – show themselves as owner of both the new phone and the money used to buy it
