An access token is a string of characters that is used to authenticate a user or an application when making requests to an API. In the context of geocoding APIs, an access token is used to identify the user or application that is making the request and to ensure that they have the necessary permissions to access the geocoding service.

Access tokens are typically generated by the API provider and are usually associated with a set of permissions or access rights that determine what the user or application can do with the API. These tokens are usually passed as a parameter in the API request and are used by the API to determine if the user or application is authorized to access the requested resources.

For example, a geocoding API provider may require an access token for usage of the API. A developer or an application using the API would have to create an account with the API provider, get an API key and pass the key in the request header. The API would then check the provided key, match it with the valid keys, and if it's a match it would allow the request to pass through and retrieve the geocoding data.