Explanation
Named workspaces allow conveniently switching between multiple instances of a single configuration within
its single backend. ... A common use for multiple workspaces is to create a parallel, distinct copy of a set of
infrastructure in order to test a set of changes before modifying the main production infrastructure.
Workspaces, allowing multiple states to be associated with a single configuration. The configuration still has
only one backend, but multiple distinct instances of that configuration to be deployed without configuring a
new backend or changing authentication credentials.
https://www.terraform.io/docs/state/workspaces.html

Explanation
Environment variables can be used to set variables. The environment variables must be in the format
TF_VAR_name and this will be checked last for a value. For example:
export TF_VAR_region=us-west-1
export TF_VAR_ami=ami-049d8641
export TF_VAR_alist='[1,2,3]'
export TF_VAR_amap='{ foo = "bar", baz = "qux" }'
https://www.terraform.io/docs/commands/environment-variables.html

Explanation
Terraform has detailed logs which can be enabled by setting the TF_LOG environment variable to any value.
This will cause detailed logs to appear on stderr.
You can set TF_LOG to one of the log levels TRACE, DEBUG, INFO, WARN or ERROR to change the
verbosity of the logs. TRACE is the most verbose and it is the default if TF_LOG is set to something other
than a log level name.
To persist logged output you can set TF_LOG_PATH in order to force the log to always be appended to a
specific file when logging is enabled. Note that even when TF_LOG_PATH is set, TF_LOG must be set in
order for any logging to be enabled.

Explanation
The Vault provider allows Terraform to read from, write to, and configure Hashicorp Vault.
Interacting with Vault from Terraform causes any secrets that you read and write to be persisted in both
Terraform's state file and in any generated plan files. For any Terraform module that reads or writes Vault
secrets, these files should be treated as sensitive and protected accordingly.

Explanation
https://www.terraform.io/registry/modules/publish
"The registry extracts information about the module from the module's source. The module name, provider,
documentation, inputs/outputs, and dependencies are all parsed and available via the UI or API, as well as the
same information for any submodules or examples in the module's source repository."