Write up description and add images

.gitignore

@@ -0,0 +1 @@
+.DS_Store

03-build-trigger-and-steps.md

@@ -0,0 +1,48 @@
+# Key CI/CD/Jenkins Concepts and their Usage
+
+## Configuring Build Triggers and Steps for a Job
+
+1. Add a default value for the build parameter named `MESSAGE` e.g. `Hello World!`.
+2. Create a build trigger that builds the project every minute.
+3. Add a build step that executes the shell command `echo 'Message: $MESSAGE'`. The message is value of the parameter.
+4. After a minute the first execution should have been triggered. Check the log output of the build and find the rendered message.
+5. Create another freestyle project named `downstream-job` in the same folder.
+6. Configure the initial job to execute the `downstream-job` if it was stable.
+
+<details><summary>Show Solution</summary>
+<p>
+
+Modify the existing build parameter.
+
+![String Parameter](./images/03-build-trigger-and-steps/string-parameter.png)
+
+Add the cron build trigger and the build step.
+
+![Build Trigger And Step](./images/03-build-trigger-and-steps/build-trigger-and-step.png)
+
+The output render the interpolated value of the `echo` command.
+
+```bash
+Started by timer
+Running as SYSTEM
+Building in workspace /Users/bmuschko/.jenkins/workspace/freestyle/my-freestyle-job
+[my-freestyle-job] $ /bin/sh -xe /var/folders/02/3dgzjkqj4kz0g7lnrk0w93c00000gn/T/jenkins3548490840940668236.sh
++ echo 'Message: Hello World!'
+Message: Hello World!
+Finished: SUCCESS
+```
+
+Create a new job in the same folder.
+
+![Both Jobs In Folder](./images/03-build-trigger-and-steps/both-jobs-in-folder.png)
+
+Configure the downstream job from the initial job.
+
+![Downstream Job Configuration](./images/03-build-trigger-and-steps/build-downstream.png)
+
+The downstream job indicates the upstream job.
+
+![Downstream Build Information](./images/03-build-trigger-and-steps/executed-downstream-job.png)
+
+</p>
+</details>