A subscription order, purchase order, pre-order,etc.,under which the parties agree to enter into a contract within a certain time limit in the future shall constitute a preliminary agreement. 当事人约定在将来一定期限内订立合同的认购书、订购书、预订书等，构成预约合同。 If one party fails to perform the obligation to contract as agreed in the preliminary agreement, the other party may claim liability of the party for breach of the preliminary agreement. 当事人一方不履行预约合同约定的订立合同义务的，对方可以请求其承担预约合同的违约责任。 Standard terms are terms drawn up by one party in advance for repeated use and not negotiated with the other party at the time of contracting. 格式条款是当事人了重复使用而预先拟定，并在订立合同时未与对方协商的条款。