u can pay attention to the difference between 其实，但是，可是，不过，然而，只不过，其实不然， they r the same meaning for begin learn,but,if u want communicat with the others,they r really different,there r many ways to express the same meaning,some way,the listener will be annoied,some way,they are not,some way,they will be pleased

其实 means "actually" in English. So when you say actually in English, you can say 其实 in Mandarin.

其实你很美！Actually ,you are beautiful !

it is used when you try to tell something true but others are not aware of it. in English it is equal to "but/while actually", "but/while the truth is" ,"but/while in fact", "but/while the fact is" for instance, 你们都误会他了，其实这钱不是他偷的。you all think he stole the money, but the fact is(其实) he is mistaken, he is not the stealer.

举个例子，用“其实”造句： 1.他们都说那件青花瓷很珍贵，其实那是个赝品。 They all think that Qinghua ceramic is value，but in fact，it is fake. So，in somewhere，其实 equals “in fact.” 2.就是说她其实并没有失踪? Meaning she wasn't actually missing? At there，其实 equals “actually.” 3.其实，光是能的一种形式。 As a matter of fact, light is a form of energy. So，其实 is "as a matter of fact."