A signatory is a party that signs an agreement. The signatory could be signing for themselves or as a representative of a company. Once the signatory is in place, the agreement will be legally binding and the signatory will be responsible for properly effecting the agreement by complying with all the obligations within it.
A signatory makes a party legally responsible for an agreement. If the person is signing on behalf of a company in their capacity as an employee of that company, then they would not be personally held liable for the agreement. Instead, the business that allowed them to sign the agreement on their behalf would be responsible for complying with all the terms and conditions.