Ansible is an open-source automation tool used for IT tasks such as configuration management, application deployment, and task automation. It is designed to be simple to use, yet powerful enough to automate complex multi-tier IT application environments.

1. Agentless: Ansible does not require any agent software to be installed on the nodes it manages. It uses SSH for communication, which simplifies the setup and reduces overhead.
2. Declarative Language: Ansible uses a simple, human-readable language called YAML (Yet Another Markup Language) to describe automation jobs. This makes it easy to write and understand playbooks.
3. Idempotency: Ansible ensures that the state of the system is consistent, regardless of how many times a playbook is run. This means that running the same playbook multiple times will not change the system if it is already in the desired state.
4. Extensible: Ansible can be extended with custom modules, plugins, and dynamic inventories, allowing it to be tailored to specific needs.
5. Community Support: Ansible has a large and active community that contributes modules, roles, and playbooks, making it easier to find solutions and best practices.

Ansible operates by connecting to your nodes and pushing out small programs, called "Ansible modules," to them. These programs are written to be resource models of the desired state of the system. Ansible then executes these modules over SSH and removes them when finished.

1. Inventory: Ansible keeps track of all the systems it manages through an inventory file. This file lists the nodes and groups of nodes that Ansible will manage.
2. Modules: Ansible uses modules to perform tasks. Modules are small programs that Ansible pushes out to the nodes.
3. Playbooks: Playbooks are YAML files that define a series of tasks to be executed on the nodes. They are the core of Ansible's configuration, deployment, and orchestration language.
4. Execution: Ansible connects to the nodes via SSH, executes the tasks defined in the playbooks, and ensures the nodes are in the desired state.

Let's look at a simple example to understand how Ansible works. We'll create a basic playbook to install Apache on a remote server.

Create an inventory file named hosts:

Create a playbook named install_apache.yml:

• Inventory File: The inventory file lists the IP address of the web server under the [webservers] group.
• Playbook: The playbook install_apache.yml contains a single play that targets the webservers group. It uses the apt module to ensure that Apache (apache2) is installed on the server.

To run the playbook, use the following command:

This command tells Ansible to use the hosts inventory file and execute the install_apache.yml playbook.

In this section, we introduced Ansible, an open-source automation tool used for configuration management, application deployment, and task automation. We discussed its key features, how it works, and provided a practical example of using Ansible to install Apache on a remote server. Understanding these basics sets the foundation for diving deeper into Ansible's capabilities in the subsequent modules.