We brush up on something, it means to update or improve yourself.

我们复习一些东西，意味着更新或提高自己。

Ariel wants to know the difference the expression " to brush up on (something)" and " to polish up" .

Ariel 想知道“to brush up on (something)”和“to polish up”的区别。

When we brush up on something, you think with a brush you put strokes down, and you can improve if you're doing a painting or something, yeah?

当我们刷东西时，你会认为用画笔你把笔触放下来，如果你在画画什么的，你可以改进，是吗？

Usually these two expressions, then, are used in the same way, but " to brush up on" something implies that you had a skill that was good once, but it's been many years or a long time since you've used it.

通常这两个表达方式， 然后，以相同的方式使用，但是“to brush up on” something 意味着你有一个曾经很好的技能， 但是你已经很多年或很长时间没有使用它了。

" To brush up on (something)" means to practice or to pick up a skill or talent that you have already acquired – you have already achieved, but you haven't used for a long time, and therefore it may need some work.

" to brush up on (something)" 意思是去练习或学习你已经获得的技能或天赋——你已经达到了，但你已经很久没有使用了，因此可能需要一些工作。