如果它看着像只鸭子，走路像只鸭子，叫声像只鸭子，那它一定是只鸭子。This is what I got from wikipedia-It is sometimes used to counter abstruse arguments that something is not what it appears to be. Is it the deep underlying meaning you mean?

Life is not easy,Humor is art. Are you a teacher?Hou about you speak Chinese?

O.K, yes, as 暗水蓝月Scarlett said, this is used to counter the argument, that things are not always as they appear. All too often people will try to say there must be another reason something happened, that the real reason is not the only possibility. This duck saying is often used when talking about people, yes, sometimes bad people who are always doing nasty things, saying nasty stuff etc will not be like that, but people tend to always try and say he/she is not really like that, so then someone will say, you know? If it looks like a duck, walks like a duck, and quacks like a duck, it must be a duck! Maybe yes, this person is just really a nasty person!

你翻译对了，但是，翻译的是句子的表面意思。没有进一步的解释翻译它的含义。你可以试着再翻译一下它的含义

Yea, off course, we are curious about its meaning.