Sometimes there is a scenario where you will want a managed node in your inventory to get a fact about the other managed nodes in your inventory. For example, the ansible_default_ipv4.address fact will display each managed nodes IP address. 

---
- hosts: all
  tasks:
  - name: display IP address
    debug:
      msg: "{{ ansible_default_ipv4.address }}"
...

The following should be returned. Notice the IP addresses are different, because the IP address of each managed node is being returned.

ok: [server1.example.com] => {
    "msg": "192.168.0.7"
}
ok: [server2.example.com] => {
    "msg": "192.168.0.11"
}
ok: [server3.example.com] => {
    "msg": "192.168.0.15"
}

hostvars can be used to get the fact of some other managed node in your inventory. Since hostvars displays facts, the gather_facts module must be set to true, which is the default setting of the gather_facts module. In other words, the gather_facts module must not be set to false.

---
- hosts: all
  tasks:
    - name: display server2 IP address
      debug:
        msg: "{{ hostvars['server2.example.com']['ansible_default_ipv4']['address'] }}"
...

Something like this should be returned. Notice that 192.168.0.11 is being returned, which is server2 IP address.

TASK [display server2 IP address] 
ok: [server1.example.com] => {
    "msg": "192.168.0.11"
}
ok: [server2.example.com] => {
    "msg": "192.168.0.11"
}
ok: [server3.example.com] => {
    "msg": "192.168.0.11"
}