The phrase "That's what she said" is a type of innuendo or double entendre commonly used in English-speaking cultures. It's a form of humor where a statement that is innocent or straightforward on the surface can be interpreted in a suggestive or sexual way when taken out of context.
The phrase is often used as a punchline after someone unintentionally says something that can be interpreted in a sexual or risqué manner. When another person responds with "That's what she said," it implies that someone else (referred to as "she") made a similar suggestive comment earlier. It's a way to playfully highlight the unintended sexual connotation of the previous statement, adding a touch of humor to the conversation.
The phrase gained widespread popularity due to its frequent use in the American version of the TV show "The Office," where the character Michael Scott (played by Steve Carell) often used it for comedic effect.
It's important to note that while this phrase can be lighthearted and humorous among friends in certain contexts, it can also be considered inappropriate or offensive in more formal or professional settings. So, it's essential to use this kind of humor with caution and be mindful of the audience and the context in which it's used.