Packer is an open-source tool for creating machine images or artifacts that can be used to provision and configure virtual machines, containers, or other infrastructure platforms. It allows developers and system administrators to automate the process of building and deploying consistent, pre-configured environments across different cloud providers or virtualization platforms. Packer uses a declarative configuration language to define the desired state of the image and the steps required to create it.

With Packer, users can define a set of builders that specify the source platform, such as Amazon Web Services (AWS), Microsoft Azure, or Docker. Packer supports a wide range of builders, enabling users to create machine images for different platforms using a single configuration. During the image building process, Packer provisions and configures the image according to the specified configuration, installing packages, configuring software, and running scripts as necessary.

Packer also provides the ability to create reusable components called "provisioners" that enable further customization of the image. Provisioners allow users to run additional configuration management tools or execute scripts to install software or perform other tasks. Packer supports popular configuration management tools such as Ansible, Chef, and Puppet.

By using Packer, organizations can ensure consistent, repeatable, and version-controlled image creation processes. It enables the creation of standardized environments that can be easily replicated and deployed, reducing the risk of configuration errors and improving overall efficiency in deploying infrastructure.