What does Signature mean?
A signature on the blockchain is a mathematical operation that allows them to prove that they have ownership over their coins, wallet, data, or anything else on the blockchain.
It is the private key that is used to provide the signature to the network, verifying that a transaction is valid.
Because the private key can provide a signature to the network it is critical that it be kept secret from everyone you don’t wish to gain control over your cryptocurrencies. Signatures are theoretically mathematically impossible to hack.