我不太懂英语,看到一本英语字典说am的过去式是was,过去分词是been,那个been又是在什么情况下使用?请用自己的话回答,我更易看懂.

be 动词包括：am , is , are , was, were,
am 的过去式是：was 用于过去时态；
过去分词been 用于现在或过去完成时态.
例如：
I am a student now.
I was a student last year.
I have been to beijing before.
He said he had been to there before.