What is the difference between image vs service in gitlab-ci?

Question

Continuous Integration

Please explain the difference between image (image) and service (service) in gitlab-ci.yml.
The service indicates on which runner (runner) the job can work, and image in which container the code of the job will be executed?
Off. dock

Answer 1

Read the entire doc, there are examples of what service is good for/not good for.
image - yes, the job code will be executed there. For example, it can be any container with a base linux image. Or, for example, an npm container if you are building/testing a Nodejs application.
service is some additional container(s) linked to the main one. Services (overwhelmingly, network services) are most needed at the testing stage, because your application for work may need, for example, a database, as discussed in the dock examples