type_debug is a filter that can be used to determine if the value stored in a variable is a boolean, an integer, unicode, AnsibleUnsafeText, AnsibleUnicode, or AnsibleVaultEncryptedUnicode.

• AnsibleUnsafeText = a string, such as Hello World
• AnsibleUnicode = a string, such as Hello World
• AnsibleVaultEncryptedUnicode = a string encrypted by the ansible-vault command
• boolean = true, false, yes, no, 1, 0
• integer = a number other than 1 or 0, such as 123456
• unicode = a string, such as Hello World

For example, lets say you have the following playbook. 

---
- hosts: localhost
  vars:
    my_string: "hello"
    my_list: ['foo', 'bar']
    my_boolean: true
    my_integer: 123
  tasks:
  - shell: ps
    register: out

  - set_fact:
      set_fact_register_out: out

  - debug:
      var: my_string | type_debug

  - debug:
      var: my_list | type_debug

  - debug:
      var: my_boolean | type_debug

  - debug:
      var: my_integer | type_debug

  - debug:
      var: out | type_debug

  - debug:
      var: set_fact_register_out | type_debug

  - debug:
      var: my_extra_variable | type_debug
...

Something like this should be returned.

TASK [debug]
ok: [localhost] => {
    "my_string | type_debug": "AnsibleUnicode"
}
TASK [debug]
ok: [localhost] => {
    "my_list | type_debug": "list"
}

TASK [debug]
ok: [localhost] => {
    "my_boolean | type_debug": "bool"
}

TASK [debug]
ok: [localhost] => {
    "my_integer | type_debug": "int"
}

TASK [debug]
ok: [localhost] => {
    "out | type_debug": "dict"
}

TASK [debug]
ok: [localhost] => {
    "set_fact_register_out | type_debug": "AnsibleUnicode"
}

TASK [debug]
ok: [localhost] => {
    "my_extra_variable | type_debug": "unicode"
}