What is the role of a private key in a blockchain wallet?

A private key is a secret code that is associated with a public key and is used to access and manage the cryptocurrencies stored in a blockchain wallet. Essentially, it is the password that grants access to the funds stored in a wallet. When a user sends a transaction using their blockchain wallet, the private key is used to sign the transaction and validate its authenticity. Since the private key provides complete control over the wallet and its contents, it is important to keep it safe and secure, and never share it with anyone.