Explanation
https://www.terraform.io/docs/modules/sources.html#selecting-a-revision

The terraform validate command validates the configuration files in a directory, referring only to the configuration and not accessing any remote services such as remote state, provider APIs, etc.
Validate runs checks that verify whether a configuration is syntactically valid and internally consistent, regardless of any provided variables or existing state. It is thus primarily useful for general verification of reusable modules, including the correctness of attribute names and value types.
It is safe to run this command automatically, for example as a post-save check in a text editor or as a test step for a re-usable module in a CI system.

Explanation
For production use, you should constrain the acceptable provider versions via configuration file to ensure that new versions with breaking changes will not be automatically installed by terraform init in the future.
Example
terraform {
required_providers {
aws = ">= 2.7.0"
}
}

terraform init command is used to initialize a working directory containing Terraform configuration files. Reference: https://www.terraform.io/docs/cli/commands/init.html