strapi/website/documentation/concepts/services.md

Services

Services can be thought of as libraries which contain functions that you might want to use in many places of your application. For example, you might have an sendEmail service which wraps some default email message boilerplate code that you would want to use in many parts of your application.

For example you can generate a service named sendEmail for the email API using the CLI:

$ strapi generate:service sendEmail email