---
layout: docs
page_title: Glossary of Terms
sidebar_title: Glossary
description: |-
  Vault Glossary.
---

# Glossary

This page collects brief definitions of some of the technical terms used in the
documentation for Vault.

- [Audit Device](#audit-device)
- [Auth Method](#auth-method)
- [Barrier](#barrier)
- [Client Token](#client-token)
- [Plugin](#plugin)
- [Secret](#secret)
- [Secrets Engine](#secrets-engine)
- [Server](#server)
- [Storage Backend](#storage-backend)

### Audit Device

An audit device is responsible for managing audit logs.
Every request to Vault and response from Vault goes through the configured
audit devices. This provides a simple way to integrate Vault with multiple
audit logging destinations of different types.

### Auth Method

An auth method is used to authenticate users or applications
which are connecting to Vault. Once authenticated, the auth method returns the
list of applicable policies which should be applied. Vault takes an
authenticated user and returns a client token that can be used for future
requests. As an example, the `userpass` auth method uses a username and
password to authenticate the user. Alternatively, the `github` auth method
allows users to authenticate via GitHub.

### Barrier

Almost everything Vault writes to storage is encrypted using the keyring, which is protected by the seal. We refer to this practice as "the barrier". There are a few exceptions to the rule, for example, the seal configuration is stored in an unencrypted file since it's needed to unseal the barrier, and the keyring is encrypted using the root key, while the root key is encrypted using the seal.

### Client Token

A client token (aka "Vault Token") is conceptually
similar to a session cookie on a web site. Once a user authenticates, Vault
returns a client token which is used for future requests. The token is used by
Vault to verify the identity of the client and to enforce the applicable ACL
policies. This token is passed via HTTP headers.

### Plugin

Plugins are a feature of Vault that can be enabled, disabled, and customized to
some degree. All Vault [auth methods](/vault/docs/auth) and [secrets engines](/vault/docs/secrets)
are considered plugins.

#### Built-in Plugin

Built-in plugins are shipped with Vault, often for commonly used
implementations, and require no additional operator intervention to run.
Built-in plugins are just like any other backend code inside Vault.

#### External Plugin

External plugins are not shipped with Vault and require additional operator
intervention to run. Vault's external plugins are completely separate,
standalone applications that Vault executes and communicates with over RPC.
Each time a Vault secret engine or auth method is mounted, a new process is
spawned.

#### External Multiplexed Plugin

An external plugin may make use of [plugin multiplexing](/vault/docs/plugins/plugin-architecture#plugin-multiplexing).
A multiplexed plugin allows a single plugin process to be used for multiple
mounts of the same type.

### Secret

A secret is the term for anything returned by Vault which
contains confidential or cryptographic material. Not everything returned by
Vault is a secret, for example system configuration, status information, or
policies are not considered secrets. Dynamic secrets always have an associated lease, and static secrets do not.
This means clients cannot assume that the dynamic secret contents can be used
indefinitely. Vault will revoke a dynamic secret at the end of the lease, and an
operator may intervene to revoke the Dynamic Secret before the lease is over. This
contract between Vault and its clients is critical, as it allows for changes
in keys and policies without manual intervention.

### Secrets Engine

A secrets engine is responsible for managing secrets.
Simple secrets engines, such as the "kv" secrets engine, return the same
secret when queried. Some secrets engines support using policies to
dynamically generate a secret each time they are queried. This allows for
unique secrets to be used which allows Vault to do fine-grained revocation and
policy updates. As an example, a MySQL secrets engine could be configured with
a "web" policy. When the "web" secret is read, a new MySQL user/password pair
will be generated with a limited set of privileges for the web server.

### Server

Vault depends on a long-running instance which operates as a
server. The Vault server provides an API which clients interact with and
manages the interaction between all the secrets engines, ACL enforcement, and
secret lease revocation. Having a server based architecture decouples clients
from the security keys and policies, enables centralized audit logging, and
simplifies administration for operators.

### Storage Backend

A storage backend is responsible for durable storage of
_encrypted_ data. Backends are not trusted by Vault and are only expected to
provide durability. The storage backend is configured when starting the Vault
server.
