从词来看
大部分的过去式和过去分词是一个词 少部分的不同
从用法来看
过去式是用于一般过去式 做谓语.
例：She went to school yesterday.
过去分词：
1.用于完成时,与have和had分别构成现在完成（进行 时和过去完成（进行）时,做谓语.
例：She has gone to school.
2.与be或should have等等构成被动语态.
例：He is beaten by his father.
3.非谓语动词之一,表示被动,完成的意思,可作定语,表语,补语和状语.
例：The boy beaten by his father is my friend.
beaten by his dad,he leave his home because of anger.