Explain the difference between `before_script`, `script`, and `after_script`.

These are execution phases within GitLab CI jobs:

• before_script: Runs before the main script, used for setup tasks
• script: Main commands to execute (required)
• after_script: Runs after script completion, regardless of job success/failure

Example:

job-example:
  before_script:
    - echo "Setting up environment"
    - apt-get update
  script:
    - echo "Running main commands"
    - npm test
  after_script:
    - echo "Cleaning up"
    - rm -rf temp/

Important: after_script always runs, making it ideal for cleanup tasks, while before_script failure will fail the entire job.