In this example, the user created a `modules` directory and then saved the module in that new directory. Therefore, the answer is in the modules subdirectory in the current working directory where Terraform is being executed.

Anytime you have a local path as the source, the module will be sourced from the referenced directory. You could also put the path of a VCS repository here, or a reference to a private or public module registry.

For example, if you wanted to reference a public module, you could use something like this:

module "network" {

 source = "Azure/network/azurerm"

 version = "3.5.0"

 # insert the 1 required variable here

}

https://www.terraform.io/internals/module-registry-protocol#module-addresses

You don't have to specify a provider block since Terraform is smart enough to download the right provider based on the specified resources. That said, Terraform official documentation states that Terraform configurations must declare which providers they require so that Terraform can install and use them. Although Terraform CAN be used without declaring a plugin, you should follow best practices and declare it along with the required_version argument to explicitly set the version constraint.

https://www.terraform.io/language/providers/requirements

Trace is the most verbose logging level. In order, they go TRACE, DEBUG, INFO, WARN and ERROR

https://www.terraform.io/internals/debugging

In order to properly and correctly manage your infrastructure resources, Terraform stores the state of your managed infrastructure. Terraform uses this state on each execution to plan and make changes to your infrastructure. This state must be stored and maintained on each execution so future operations can perform correctly.

During execution, Terraform will examine the state of the currently running infrastructure, determine what differences exist between the current state and the revised desired state, and indicate the necessary changes that must be applied. When approved to proceed, only the necessary changes will be applied, leaving existing, valid infrastructure untouched.

By default, Terraform will store the state in a JSON-formatted file named terraform.tfstate in the current working directory. The file should never be modified directly if state needs to be manually changed. You should use the terraform state command to modify state where possible.

The local state file is NOT encrypted (unless your local disk is encrypted or using something like Windows Bitlocker). This is why many organizations use a remote backend, which will store the state file in an encrypted store. This also allows multiple team members to work with the state file rather than storing it on an individual's laptop/desktop.

https://www.terraform.io/language/state

If supported by your backend, Terraform will lock your state for all operations that could write state. This prevents others from acquiring the lock and potentially corrupting your state.

State locking happens automatically on all operations that could write state. You won't see any message that it is happening. If state locking fails, Terraform will not continue. You can disable state locking for most commands with the -lock flag but it is not recommended.

https://www.terraform.io/language/state/locking

Input variables (commonly referenced as just 'variables') are often declared in a separate file called `variables.tf`, although this is not required. Most people will consolidate variable declaration in this file for organization and simplification of management. Each variable used in a Terraform configuration must be declared before it can be used. Variables are declared in a variable block - one block for each variable. The variable block contains the variable name, most importantly, and then often includes additional information such as the type, a description, a default value, and other options.

The value of a Terraform variable can be set multiple ways, including setting a default value, interactively passing a value when executing a terraform plan and apply, using an environment variable, or setting the value in a `.tfvars` file. Each of these different options follows a strict order of precedence that Terraform uses to set the value of a variable.

A huge benefit of using Terraform is the ability to reference other resources throughout your configuration for other functions. These might include getting certain values needed to create other resources, creating an output to export a specific value, or using data retrieved from a data block. Most of these use dot-separated paths for elements of object values.

The following represents the kinds of named values available in Terraform:

   * <RESOURCE TYPE>.<NAME> represents a managed resource of the given type and name.

   * var.<NAME> is the value of the input variable of the given name.

   * local.<NAME> is the value of the local value of the given name.

   * module.<MODULE NAME> is a value representing the results of a module block.

   * data.<DATA TYPE>.<NAME> is an object representing a data resource of a given type and name

   * Additional named values include ones for filesystem and workspace info and block-local values

https://www.terraform.io/language/expressions/references#input-variables

The terraform apply command executes the actions proposed in a Terraform plan. This works the same regardless of whether you have existing infrastructure deployed and changes are needed, or if you are just deploying your infrastructure for the first time. The terraform apply command can also destroy infrastructure by passing the -destroy flag as well.

WRONG ANSWER:

Running a terraform apply cannot import infrastructure to pull under Terraform management. That's the job of the terraform import command

https://www.terraform.io/cli/commands/apply

https://learn.hashicorp.com/collections/terraform/aws-get-started

The terraform console command will read the Terraform configuration in the current working directory and the Terraform state file from the configured backend so that interpolations can be tested against both the values in the configuration and the state file.

When you execute a terraform console command, you'll get this output:

$ terraform console

Acquiring state lock. This may take a few moments...

>

https://www.terraform.io/cli/commands/console