Describe what you need in a file
A team writes files describing the servers, databases, and networks it needs. A tool reads the files and creates or updates those resources in the cloud. The files are instructions; the servers and databases still run on real computers.
Terraform and AWS CloudFormation are examples. Terraform works with different cloud providers; CloudFormation works with AWS.
Teams can keep the files in version control to review changes and track who made them. They can also use the same files to set up test and live systems consistently.
Changes still need care
A mistake in a file can delete a resource or let the wrong people access it, so teams check changes before applying them. If someone changes a resource without updating the files, the files no longer match what exists. This difference is called drift.