What is a token in the context of access permissions?

In the context of access permissions, the most fitting description is that a token refers to a gadget that displays passcodes. Tokens are commonly used in two-factor authentication systems, where they generate time-sensitive passcodes that a user must input to gain access to a secure system. This additional layer of security ensures that even if a password is compromised, unauthorized access is still prevented because the token generates unique codes that are only valid for a short period.

Given this context, the other choices, while they might hold some relevance in security, do not capture the specific function of a token in relation to access permission. A device the size of a credit card could describe various types of hardware but lacks specificity to digital authentication. A type of smart card may refer to a broader category of security credentials that could include tokens, but smart cards often serve different purposes. An electronic marker attached to a file doesn't represent a token in the standard sense associated with access permissions but rather suggests something that might indicate identity or status of data rather than being a tool for authentication.