Thinker is a Generative Pre-trained Transformer (GPT) that functions on top of the ChatGPT framework. The unique selling point of this AI tool is its ability to generate what could be called 'secret thoughts'. While it shares foundational attributes with the parent ChatGPT, it adds an additional layer by providing what appears to be an internal thought process. Just like ChatGPT, Thinker is capable of generating human-like text, with the added layer of providing some insight into an artificial thought process. To interact with the Thinker tool, a subscription to ChatGPT Plus is required, signifying that it is a more advanced feature of this platform. It uses prompt starters to initiate contextual dialogues or discussions. Although the 'secret thoughts' feature is not fully explained, it could potentially offer users greater insight and depth into the AI's text generation process by exposing some of its working logic, decisions and steps.