Digital signatures provide confidentiality, integrity, and authenticity for digital documents and communications. They use public and private key cryptography, with the private key only known to the signer. A digital certificate issued by a trusted third party binds the signer to their public key. Digital signatures are created by encrypting a hash of the message contents with the private key, allowing anyone with the public key to verify the signature and authenticator of the signed document. They can be used for secure email, computer access, software protection, and identity verification in business applications.