Laughing at an inside joke（为心里的笑话发笑）
Mom,forget it.You'll never understand it.It's an inside joke .
妈妈,算了.你永远也不会明白的,这是一个圈儿内的笑话.
We're not going to tell you what we're talking about.It's an inside joke .
我们不会告诉你我们所说的内容,这是圈儿内的秘密.