I don't understand at what are there.
Signing means applying a cryptographic operation (in the case of signing, moving a point on an elliptic curve. In Ethereum, that point is the raw (unsigned) transaction) that confirms the authenticity of the transaction by the signing party.
Given the transaction, its signature and the signer's public key, any party can check for the transaction's authenticity. Authenticity means that only the signer could have signed the respective transaction.