The concept of token has several meanings.
A token is a code – usually consisting of a small number of data or characters – that can be used as digital evidence for authentication purposes, for example when generating one-time passwords or when using 2FA.
In the context of generative AI (GenAI) the term token refers to a piece of text that the model uses as a building block in processing or generating language. A token can be a word, part of a word, or even a punctuation mark — depending on how the model is trained and what tokenizer it uses. For most AI models, a 'token' is the unit by which the cost of using it is determined, both for the input (think of a prompt) if the output.
See 2FA, Two factor authentication, generative AI, tokenizer, Time to First Token (TTFT)