What is variable substitution in Ansible?

Variable substitution in Ansible refers to the process of replacing variables defined in a playbook or inventory with their corresponding values during the execution of tasks. This allows for dynamic configuration and customization of playbooks, making them more flexible and reusable.

For example, if you define a variable in your playbook like this:

vars:
  message: "Hello, Ansible!"

You can use variable substitution to reference this variable in a task:

- name: Print a message with variable substitution
  debug:
    msg: "{{ message }}"

When the playbook runs, {{ message }} will be replaced with "Hello, Ansible!", allowing you to easily change the output by modifying the variable's value.