it means the extra requirements to you.

Its refers to this sentence "Terms and condition applies". Usually refers to attached terms.

就是如果做这件事的话，要有另外一个条件才可以。

就是还有别的条件。。比如：我今天请你去吃饭，“附带条件”是你必须带上你的孩子。。

Is it "additional condition?"