An API token acts like a permanent password for you to connect to an API. API connections are handled this way due to that fact that usernames and passwords may change, then instead of needing to change connection settings within the API, the token will remain constant.
This guide will assist you in creating, viewing and deleting an API token.
From your login screen click on the Tools tab. You will then be taken to the Tools page. From this page hold you mouse over Create > Create API Token as pictured below and click on the selected option.