What is the difference between 'terraform apply' and 'terraform plan'?

The distinction between 'terraform apply' and 'terraform plan' is fundamental to how Terraform operates when managing infrastructure as code. When you use 'terraform plan', Terraform analyzes the current state of your infrastructure compared to the desired state defined in your configuration files. It generates a detailed report of the changes that would occur if you were to apply those configurations. This allows you to review and confirm the changes before they are made, ensuring you have full visibility and control over what will happen.

On the other hand, 'terraform apply' takes the actions generated by the planning process and performs them. This command does not merely show what will be changed; it actually enacts those changes in your infrastructure. Thus, 'terraform apply' executes the modifications, creating, updating, or deleting resources as necessary, based on the plan produced during the preceding 'terraform plan'.

While 'terraform plan' is about assessing and preparing for changes, 'terraform apply' is about implementing those changes. The correct understanding of this workflow is crucial for managing infrastructure effectively with Terraform.