* 二 (èr): This is the standard pronunciation used in most situations.
* 两 (liǎng): This is used specifically when counting things, especially when referring to a number between one and ten.
So, if you are talking about "two apples", you would say "两 (liǎng) 个 苹果 (píngguǒ)". But if you are talking about "the number two", you would say "二 (èr)".