Fall for something意为allow oneself to be persuaded by something，相信某事。

例：

The salesman said the car was in good condition, and I was foolish enough to fall for it.

推销员说这辆汽车状况良好， 而我竟傻到信以为真。

例：

I'm surprised you fell for that trick.

真不敢想象你居然相信这个骗局。

Fall for somebody也就是fall in love with somebody，被某人所吸引，爱上某人，迷恋某人。

例：

They met, fell for each other and got married six weeks later.

他们俩一见倾心，6个星期后就结了婚。