If you are not familiar with modules, check out Ansible - Getting Started with Modules.
Typically, the shell, command, or script modules are used to invoke a command on a managed node. However, /usr/bin/python needs to exist on the managed node to use these modules. If Python does not exist, the raw module can be used instead. The raw module does not use Python. Typically, the raw module is used to install Python so that the shell, command, and script modules can be used.
- name: install Python using raw raw: yum -y install python
If changed is displayed, this means that Python was successfully installed on the control node (e.g. the target host).
TASK [install Python using raw] changed: [server1.example.com]