It was quite different from what I expected.它和我原来想的很不一样.这里的from是做什么的啊?他整句改成It and i expected was quite different

different from... 和...不一样
不能说：It and i expected was quite different 。
可改成：What I expected was quite different.

different from... 和...不一样,固定搭配要死记硬背
Different from and different than are both common in British and American English. Critics since the 18th century have singled out different than as incorrect, though it is well attested in the works of reputable writers. Where the comparison is drawn directly between two persons or things, from is usually the safer choice:
Different from 和 different than 英语和美语中都经常见。 虽然后者经常出现在名作家的作品中，但18世纪以来，评论家仍指出different than 为相对正确的选择。 当直接对两人或两物进行比较时，from 是最保险的选择 ：
My book is different from (not than ) yours.
我的书不同于（不是 than ） 你的。 But different than is more acceptably used, particularly in American usage, where the object of comparison is expressed by a full clause:
但different than 的比较对象用一完整的句子表示，特别是在美语用法中，这种用法更能接受：
The campus is different than it was 20 years ago (or
校园和二十年前不一样了（或
The campus is different from how it was 20 years ago).
校园和二十年前的样子不一样了）。
As a result, a simple noun phrase following different than is often construed as elliptical for a clause, which allows for a subtle distinction in meaning between the two constructions.
那么，接在different than 后的简单名词可以解释为是完整句子的省略。 两种结构在意思上有些细微的差别。
How different this seems from Paris suggests that the object of comparison is the city of Paris itself,
这与巴黎看起来有何不同呢？比较的对象是巴黎这座城市本身，
whereas
而
How different this seems than Paris suggests that the object of comparison is something like “the way things were in Paris” or “what happened in Paris.” ·
这儿与巴黎有何不同？这里比较的对象是“在巴黎的方式”或“在巴黎发生的事情”。
The construction different to is chiefly British.
结构different to 主要用于英国
It and i expected was quite different
呵呵,典型的中国式英语,可以看出你是个初学者
and是个连词,没有对所连接的前后成分进行比较的意思

different from... 和...不一样
不能说：It and i expected was quite different .
可改成：What I expected was quite different.