Pipeline configuration begins with jobs:

• Jobs are the most fundamental element of a pipeline and are executed by GitLab Runners
• Jobs are created with constraints, which govern under what conditions they should be executed
• Jobs are top-level elements that can have an arbitrary name and must contain the script element as a minimum requirement
• There can be an unlimited number of jobs

In the pipeline overview, you'll find several jobs. They have a status, an ID, are part of a stage, and have a name, as shown in the following screenshot:

You can create jobs by adding them to a configuration file called .gitlab-ci.yml. We will discuss this file in more depth in the following section.

An example of a pipeline containing two jobs is as follows:

job1:
 script: "execute-this-script-for-job1"
job2:
 script: "execute-this-script-for-job2"

The preceding example is a basic CI/CD pipeline that consists of two named jobs (job1 and job2), which execute a script section (in our example, this does nothing). In the script section, you can specify a command, script, or a chain of commands. For instance, to build a JavaScript, you can set script as npm build or run a shell unit test called unit-test.sh.

Jobs are not run on the GitLab application server, but are picked up by GitLab Runners. The runners execute the jobs in their own environment; for example, runner A can build job1 and runner B can build job2. Note that the jobs are independent from each other. The results from these jobs are aggregated on the GitLab server.