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.

Namespaces are isolated environments that functionally exist as "Vaults within a Vault." They have separate login paths and support creating and managing data isolated to their namespace. This data includes the following:
- Secret Engines
- Auth Methods
- Policies
- Identities (Entities, Groups)
- Tokens
Reference link:- https://www.vaultproject.io/docs/enterprise/namespaces

The Transit engine supports the versioning of keys. Key versions that are earlier than a key's specified min_decryption_version gets archived, and the rest of the key versions belong to the working set. This is a performance consideration to keep key loading fast, as well as a security consideration: by disallowing decryption of old versions of keys, found ciphertext corresponding to obsolete (but sensitive) data can not be decrypted by most users, but in an emergency, the min_decryption_version can be moved back to allow for legitimate decryption.
Reference link:- https://www.vaultproject.io/docs/secrets/transit

The lease command groups subcommands for interacting with leases attached to secrets.
Subcommands:
renew Renews the lease of a secret
revoke Revokes leases and secrets
Using the '-prefix' flag allows you to revoke the entire tree of secrets.

The root token should never be used on a day-to-day basis and should always be revoked once a permanent auth method has been configured.