Think of a door that only the people inside are allowed through. Behind it is the one thing that explains how the product is really made. What is sold outside is ordinary; what stays behind the door is the reason it works. Keeping the door shut is the whole point.
Two branches
公司的機密：門後面那套做法
核心畫面本來的樣子：門是真的，門後面是公司的配方或製程。
noun · B2
A piece of secret information inside a business, such as how it makes its product, that only the people who work there know. Firms keep it hidden because it gives them an edge, and the law treats it as something they own.
商業機密
日常的玩笑：我的獨門秘方
同一扇門被搬到廚房或書桌前面，語氣整個變輕。
noun · B2
A way of doing or making something that you would rather keep to yourself — said in a light, joking way about things like a recipe, a study trick or a cleaning method.
獨門秘方