A private key in the crypto space can be defined as the combination of letters and numbers that corresponds to a specific public key. The private key can be used to gain access to the assets on that public key, also known as the wallet address. Once you share your private key with somebody, store it on your computer in plain text or type it in a website or app, you risk losing all your funds stored on its a corresponding public address.
Private key
Private key Explainer Video
What is a Private Key? | Crypto Terms Explained