Ansible does apply variable precedence, and you might have a use for it. Here is the order of precedence from least to greatest (the last listed variables override all other variables):

      command line values (for example, -u my_user, these are not variables)
      role defaults (defined in role/defaults/main.yml) 1
      inventory file or script group vars 2
      inventory group_vars/all 3
      playbook group_vars/all 3
      inventory group_vars/* 3
      playbook group_vars/* 3
      inventory file or script host vars 2
      inventory host_vars/* 3
      playbook host_vars/* 3
      host facts / cached set_facts 4
      play vars
      play vars_prompt
      play vars_files
      role vars (defined in role/vars/main.yml)
      block vars (only for tasks in block)
      task vars (only for the task)
      include_vars
      set_facts / registered vars
      role (and include_role) params
      include params
      extra vars (for example, -e "user=my_user")(always win precedence)

In general, Ansible gives precedence to variables that were defined more recently, more actively, and with more explicit scope. Variables in the defaults folder inside a role are easily overridden. Anything in the vars directory of the role overrides previous versions of that variable in the namespace. Host and/or inventory variables override role defaults, but explicit includes such as the vars directory or an include_vars task override inventory variables.

Ex: yml file

- hosts: webservers
  vars:
    http_port: 80
    base_path: http://ansibile.local/wiki
    app_path: {{ base_path }}/{{ http_port }}

Facts are variable collected each time you contact a client. It contains IP adresses, OS type, level, hardware….

You can call them on the ansible server by using the command (xml output): <cli prompt='#'> opensuse:~ # ansible -m setup localhost localhost | SUCCESS ⇒ {

  "ansible_facts": {
      "ansible_all_ipv4_addresses": [
          "10.1.3.22"
      ],
      "ansible_all_ipv6_addresses": [
          "fe80::209a:12e0:e8a7:8ea"
      ],
      "ansible_apparmor": {
          "status": "enabled"
      },
      "ansible_architecture": "x86_64",
      "ansible_cmdline": {
          "BOOT_IMAGE": "/boot/vmlinuz-4.12.14-lp151.28.91-default",

      },
      "ansible_date_time": {
          "date": "2021-09-13",
          "day": "13",
          "epoch": "1631520866",
          "hour": "10",
          "minute": "14",
          "month": "09",
          "second": "26",
          "time": "10:14:26",
          "tz": "CEST",
          "tz_offset": "+0200",
          "weekday": "Monday",
          "weekday_number": "1",
          "weeknumber": "37",
          "year": "2021"
      },

…

     "ansible_distribution": "openSUSE Leap",
      "ansible_distribution_file_parsed": true,
      "ansible_distribution_file_path": "/etc/os-release",
      "ansible_distribution_file_variety": "SUSE",
      "ansible_distribution_major_version": "15",
      "ansible_distribution_release": "1",
      "ansible_distribution_version": "15.1",