意思不同。bistro的名词解释是：小餐馆；小酒馆。bar的名词解释是酒吧；(出售饮料等的)柜台；(专售某类饮食的)小吃店，小馆子。bar还有动词和介词的词性，作及物动词时意思是禁止；阻拦，作介词时意思是除……外。

bistro例句

I've visited a bistro in Paris.

我去过巴黎的一家小酒馆。

We ate in the restaurant, as opposed to the bistro.

我们是在餐厅吃的饭，而不是在小饭馆。

They tried to create the ambience of a French bistro.

他们试图营造出法国小餐馆的那种气氛。

Instead she took me to a quiet bistro with a private table.

她带我去了一个安静的小酒馆，找了一个隐蔽的桌子。

bar例句

On the ship there are video lounges, a bar and a small duty-free shop.

船上有录像厅、一个酒吧间和一家小型免税商店。

The bar is for the use of members only.

酒吧仅供会员使用。

The students all attended, bar two who were ill.

除了两名生病，所有的学生都到了。

It's the best result we've ever had, bar none.

这是我们所取得的前所未有的最好成绩。