incoterms:international rules。incoterms concern the relation between only two parties，buyer and seller，and related to the contract of sale. the contract of sale be consider as the foundation of transaction .
delivery :physical act of bringing goods from one location to the other and indicates the transfer of relevant risks and obligations between the parties.
obligation is a forceful word which implies a legal duty to do something according to a certain agreement.
cost:主要是海内外运输费，保险费。做……事，先交……费。
risks:the ability（可能性）of an accident damage to the goods
exw : ex works (seller are free in thier works(处所有可能是仓库，工厂等)when the goods are delivered to the buyer) 卖家不负责 点货装载义务，如果在此间出事就是买方的责任。
fca: seller is free when goods are delivered to the carrier nominated by the buyer 当不止一家承运商时，当移交给第一艘船时，就完成了送货义务。no matter where the delivery happen, the seller is only responsible for loading the goods once and he is not responsible for any unloading or reloading .
fas, goods alongside the vessel nominated by the buyer at the named port of shipment .船边交货，船的距离，应该在运输工具能企及的位置里。如吊钩。
