Contract name is the object of a contract. In simple words, it is the service(s) or product(s) that a Contractee (buyer) is expecting to receive from the Contractor (seller) on the contract due date.
If you don't want to put the name of the service/product in the "Contract name" field, you can use the general purpose of the contract instead.
Example: "Web design services".
Filling this field is optional, but it may help both sides find a specific contract among others (if any).