A double spend occurs when a user is able to spend the same tokens in their wallet more than once.
It is a potential flaw that can occur with digital currencies that are setup without proper security features or consensus rules that enable users to verify transactions before they are confirmed on a database.
Blockchains solve the double spend problem by introducing consensus mechanisms like proof of work and proof of stake, which require nodes to commit computing power or stake tokens in order to validate transactions before they are added to the ledger, ensuring that the state of the ledger is correctly updated to reflect the latest transactions and wallet balances.
