Access token
An access token is a secret code that lets a program act as you on a service, for a limited time or a limited job.
In a simple example
When you connect your site to your code account, the service gives a token. Your site shows it each time it asks for something.
Why it matters to you
It works like a spare key to your account, so a leaked token lets a stranger in.
Do not confuse with
An access token is a secret key. An AI token is only a piece of text that is counted.