Grails services are abstractions used for implementing business logic (as well as connecting to backing services/DBs, etc.) outside of a controller. So in a typical controller y
You can also get a service using grails.util.Holders
grails.util.Holders
Example:
For injecting MyService service class, use Holders.applicationContext.getBean("myService")
Holders.applicationContext.getBean("myService")
Where "myService" is the name of your service class in lower camel case.