1.经济补偿金
Severance Pay
An allowance usually based on length of service that is payable to an employee on termination of employment.
[Merriam-Webster’s Collegiate]
中国法律环境下的理解:用人单位依法在合同有效期内解除劳动合同给付劳动者的一种补偿;是企业单方面行为;且是法定的;是劳动合同解除后发生的. 一般是按员工工作年限支付。

2.赔偿金 
Damages
The pecuniary compensation awarded by the court to an innocent party to an action, the objective of which is to compensate the loss actually suffered by the innocent party and not what the wrongdoer should reasonably pay. [LexisNexis] 
damages:In law, the money awarded to a party in a civil suit as reparation for the loss or injury for which another is liable.[Britannica Concise Encyclopedia] 
中国法律环境下的理解:当事人因违反合同约定或自己的失误，给对方造成实际损失，对此损失的赔偿,是双方行为;按实际损失确定. 比如:盗窃,破坏设备等,公司有权要求员工承担赔偿责任。

3.违约金 
Liquidated Damages
Damages sought or awarded to a plaintiff, the amount being a sum fixed by the parties to a contract as a genuine pre-estimate of the plaintiff’s loss in the event of the defendant’s breach or ascertainable by a simple calculation or fixed by any scale of charges or other positive date. [LexisNexis] 
中国法律环境下的理解:劳动合同当事人事先约定的违约方给守约方支付的固定金额。只有在劳动合同法明确规定的情景下才可以约定违约金;只要对方违约即可,不需要有实际损失发生. 比如:员工违反培训服务期约定,提前辞职的,公司有权要求对方支付违约金。