The letter's contents were not disclosed.是什么意思？

The letter's contents were not disclosed.

信件内容并未透露。

the

art. 指已提到的人（物），指说话人与听者已知的人（物），用于独一无二的事物前，与形容词最高级和序数词连用；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

contents

n. 内容，（书、讲话、节目等的）主题，含量，所含之物( content的名词复数 )，（书等的）内容，目录，容量，含量，（书、讲话、节目等的）主题；

例句
Why are the contents of the next person's shopping trolley always more alluring than one's own?
为什么旁边人购物车里的东西看起来总是比自己车里的更诱人呢？

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

not

adv. 不，[用以表示否定、否认、拒绝、禁止等]不是，几乎不，未必，没有[用于否定后面的词或短语]；

例句
It became very clear that the incident was not just an aberration, it was not just a single incident.
事实已经很清楚，这件事不是偶发的，它并不是一起孤立的事件。

disclosed

v. 说出( disclose的过去式和过去分词 )，揭露，使显露，使暴露；

例句
A government official disclosed that they were on a secret blacklist...
一名政府官员透露他们已被列入一份秘密黑名单。