一、for sb的用法及含义
for sb，中文含义是对于某人来说或者是提供某物给某人。for是并列连词，引导的是并列从句。
例句：Undoubtedly you have mistaken me for sb else.
无疑你是认错人了。
But it was hard for sb to work it out.
但是对他来说很难抽出时间安排。
It's time for sb to do something.
是某人做某事的时间了。
It's a good idea ( for sb) to do sth.
做某事（对某人而言）是一个好主意。
I am pleased to write a letter of recommendation for sb.
很乐于写此信推荐某人。
Hope it's helpful for sb who were married or will be marry!
希望对已经结婚或将要结婚的弟兄姐妹有帮助！
二、to sb的用法及含义
to sb的'中文含义是对某人来说或者是把某物借给某人。用to的话，表示目标或目的地，是指某人或动作的承受者，to sb表示动作的运动方向。
例句：Please give my regards ( to sb.) when you write.
写信时请替我带上一笔。
Say farewell to sb is the last thing I would like.
跟任何人道别都是我最讨厌的事。
Trust a matter to sb. She take out a life insurance policy.
把某事委托给某人办理她办理了人寿保险。
Shift the responsibility or blame for sth to sb else.
将某事的责任或过失推委给别人。
Give sth to sb as a share of work to be done or of things to be used.
分配给某人一部分工作去做或一份东西去使用。