to get information about something because you want to know more about it, or to learn a fact or piece of information for the first time

How did you find out about the party? 你是怎么知道这个聚会的？

The holiday was a complete surprise - I only found out about it the day before we left. 这次度假完全是个惊喜——我是在临走前一天才得知的。

[ + question word ] I'll just go and find out what's going on outside. 我这就出去看看外面究竟在干什么。

[ + that ] Too late, she found out that the flight had been cancelled. 她发现这个航班已经被取消了，不过已经太迟了。

to discover that someone has done something wrong

He lived in fear of being found out. 他终日惶恐不安，生怕东窗事发。