What is Private key?
A private key is the secret that signs transactions for an address. Whoever holds it controls the funds, and no one can reverse or recover a transfer it authorised.
In practice
Keys should never be typed into a website, shared in a chat, or stored in plain text. No legitimate platform, including Dapping, will ever ask for a private key or seed phrase. Anyone who does is running a theft attempt, and the loss is permanent.