API Keys panel allows accessing Leon API from the interface in order to obtain a feed of different kinds of data from Leon for the purpose of outside integrations.
The functionality generates a Refresh Token, which is a special kind of token that can be used to obtain a renewed access token which allows programmatically accessing a protected resource. Access tokens are attached to API request. More information can be found in the documentation (https://bitbucket.org/leondevteam/api-documentation/src/master/).
The token can be generated only by admins in Settings → API keys page.
How to generate a token