Terraform matters because Terraform makes infrastructure reviewable and repeatable instead of click-driven. It gives builders a precise word for the thing they are changing, debugging, reviewing, or shipping.
ELI5
Think of Terraform as part of the roads and power for the app. It gives one small job a clear name so the whole app is easier to understand.
In practice
Use it when local work needs to survive hosting, networks, caching, or production traffic. In practice, name the owner, input, output, failure mode, and proof before relying on Terraform.